Bacterial Tubulin (FtsZ) and Actin (MreB) Homologues: The Spatial Organization of Bacterial Cells • iBiology

Part 1: The critical role of spatial organization in bacterial cell function

10:02.2 it's going to spontaneously self-assemble into those beautiful filaments
26:42.0 to the funding agencies that support research in bacterial cell biology.
08:37.1 now the cells still grow, but now cell wall synthesis is disorganized
24:14.3 and it was shown that the arrangement of those genes inside the cells
25:48.1 So, starting with single-molecule fluorescence microscopy techniques,
25:58.3 this is increasing the spatial resolution at which we can see things,
06:52.3 and therefore now those cells are going to form those long filaments
16:36.2 Caulobacter, when it divides, is going to produce two daughter cells
19:51.1 is going to be able to move in the cytoplasm of the eukaryotic cell,
00:29.0 the spatial organization of bacterial cells is remarkably complex,
01:39.0 But there is another difference in terms of cellular organization.
03:49.0 and intermediate filaments made of intermediate filament proteins.
14:13.2 This is going to increase the surface-to-volume ratio of the cell,
16:59.1 and in blue you have a kinase accumulating at one end of the cells
26:02.1 and for bacterial cells that are very tiny this is very important.
06:16.1 and the reason is because it's as if you were looking at the ring
10:16.0 Now, inside of cells, crescentin is also going to form filaments,
10:20.2 and what's really neat is that it's going to form those filaments
11:57.2 And this is reminiscent to all the intermediate filament proteins
15:29.1 So, there is a lot of protein at the pole with pole localization.
15:55.2 so those are the chromosomes, the chromosome has been duplicated,
11:29.2 into those tightly-coiled cells that look like a telephone cord.
19:31.2 Okay, so we're going to have polymerization and depolymerization
21:58.2 is basically oscillating from one end of the cells to the other.
25:44.2 in microscopy and microscopy-related techniques in recent years.
04:23.2 and here are the crystal structures of the eukaryotic tubulins.
05:44.0 and they're going to specifically form at the site of division,
05:49.2 this ring is going to be important for the cytokinesis process,
22:40.2 where there is the lowest concentration of that MinC inhibitor,
04:33.3 At the structural level, there is really beautiful similarity.
05:07.3 it's going to polymerize if you put it in the presence of GTP.
09:41.2 the first intermediate filament-like protein found in bacteria
12:46.2 to our intermediate filaments in our cells, in our skin cells,
12:50.1 that are important for the mechanical strength of those cells.
08:11.0 and this is going to be important for the elongation process.
20:35.1 is going to be able to move into another, a neighboring cell,
21:03.3 This is the localization of a protein called MinD in E. coli,
25:35.3 and so there are many discoveries that still have to be made,
09:00.1 in particular the rod-shaped bacteria that have to elongate.
09:58.1 and a striking one is that if you purify crescentin in vitro
11:24.3 you overproduce crescentin and you also block cell division,
13:32.3 there is really a richness in terms of cytoskeletal elements
15:43.3 and it's going to achieve a lot of polarized function there.
16:28.1 And so, this is an example, again in Caulobacter crescentus,
23:56.0 and it has a typical circular chromosome like many bacteria,
00:18.0 and an investigator of the Howard Hughes Medical Institute.
00:22.3 I would like to tell you about the cell biology of bacteria
01:32.2 and so we have a big difference between eukaryotic cells...
08:07.3 is going to be guided along the circumference of the cells,
09:16.3 intermediate filament proteins that are found in our cells,
12:02.0 that are also important for different mechanical functions.
12:23.1 and it forms those filamentous structures inside the cells,
13:09.1 that are important for a variety of cytoskeletal functions.
17:14.0 actually they have opposing activity on the same regulator,
19:09.1 So, you can see that it accumulates at one end of the cell,
02:17.0 and then inside the cytoplasm is pretty much everything...
07:16.2 there is some similarity but it's not incredibly apparent,
09:27.1 made of four coil-coiled-forming segments, shown in green,
10:46.2 on one side of the cells, the side of the inner curvature.
14:31.2 that is a little bit shorter than the other daughter cell.
21:51.1 but it's also associated with another protein called MinC.
24:11.2 were localized inside of cells by fluorescence microscopy,
25:02.2 where transcription and translation are separated in time.
06:26.0 and that's going to promote cell wall synthesis across...
08:43.1 get fatter and fatter and fatter until they became round,
11:09.1 So, this is what happened when you don't have crescentin,
11:40.1 is by mechanically affecting the way that the cells grow.
15:32.1 Another example, which is here in Caulobacter crescentus,
16:03.1 because it can interact indirectly with the DNA sequence,
16:21.1 but there are also proteins that can do better than that.
17:26.2 Now, in the mother cells, so in the pre-divisional cells,
19:37.0 and this is going to allow to cells, the bacterial cells,
20:59.1 Now, those patterns can be even more intricate than that,
23:46.3 I'm going to show you the case of Caulobacter crescentus.
26:28.3 I would like to thank past and current members of my lab.
00:48.2 so, starting with our health, also with our environment,
02:49.3 Well, this was thought to be unique to eukaryotic cells.
03:57.1 counterparts to all three types of cytoskeletal systems.
10:40.0 and this is actually mediated by this protein crescentin
17:18.2 and this regulator, whether it is phosphorylated or not,
17:21.1 it's going to be able to turn on gene expression or not.
20:39.1 and thereby it's going to be able to colonize the tissue
22:53.2 I've shown you that bacteria have cytoskeletal elements,
23:59.2 with a single origin and a terminus at the opposite end.
25:52.0 and super-resolution fluorescence microscopy techniques,
02:31.3 that the eukaryotic cell has an elaborate cytoskeleton,
02:37.2 and also they can have sophisticated spatial patterning
11:37.2 the way that crescentin filaments affect cell curvature
13:21.1 and these also are important for cytoskeletal functions
16:18.0 are proteins that accumulate at both ends of the cells,
19:27.1 and by doing so it's going to create those actin tails.
22:56.2 they also exhibit spatial patterning and cell polarity,
23:44.0 Okay, so, this has been shown in many bacterial models.
25:10.1 at a predictable and conserved region inside the cells,
26:32.0 In particular, I would like to thank Jennifer Heinritz,
01:02.1 and they are absolutely essential for sustaining life,
03:21.1 and also they can exhibit intricate spatial patterning
04:30.2 there is similarity, but it's not incredibly striking.
04:43.2 the bacterial FtsZ protein and the eukaryotic tubulins
06:01.2 because FtsZ has been tagged by a fluorescent protein,
11:06.1 is important for surface adhesion in natural habitats.
17:52.2 and now the regulator is going to be unphosphorylated,
18:02.2 and therefore you're going to have a different program
19:07.1 but you would see the same thing for ActA in Listeria.
21:30.2 is that you can see this localization is very dynamic.
25:13.0 it means that the protein that is encoded by that gene
00:09.2 I am the director of the Microbial Sciences Institute
00:54.2 and so it is very important for us to study bacteria.
04:00.1 So, let's start with the tubulin homolog in bacteria.
06:57.2 So, many bacteria have a tubulin homolog called FtsZ.
09:39.0 Now, the first bacteria to make a filament protein...
09:47.0 Now, this protein was bound in Caulobacter crescentus
10:53.2 so if we delete the genes that encode for crescentin,
12:16.2 and here this is shown is Streptomyces pseudocolored,
14:25.1 division is also asymmetric, unequal, in Caulobacter,
18:20.1 is not only seen in asymmetrically-dividing bacteria.
21:46.2 oscillates through a very simple biochemical reaction
25:22.0 bacteria exhibit a sophisticated spatial organization
26:25.2 all the bacterial cell biology labs across the world.
01:43.2 through a bacterial cell and through an animal cell,
01:53.3 So, in the bottom you have a typical eukaryotic cell
04:12.2 because it's absolutely essential for cell division.
08:57.1 So, you have... some bacteria have an actin homolog,
09:49.1 and, again, it has the same structural organization.
18:10.1 because of this asymmetric localization of proteins,
20:18.0 Well, this is what's going to promote those bacteria
23:00.2 but there is another element of spatial organization
23:53.2 so, this is the chromosome of Caulobacter crescentus
26:17.2 to study the cell biology of bacteria in the future.
00:35.0 is very important for the behavior and the function
03:27.2 so, there's been a lot of evidence in recent years.
03:30.1 I won't have time to describe all of this evidence,
05:23.0 are going to associate underneath the cell membrane
05:30.1 So, this is looking at a cross-section of the cell.
07:48.1 that are going to be just beneath the cell membrane
15:24.0 proteins that accumulate at the end of the cells...
19:00.2 and this is shown in this electron micrograph here,
24:29.3 whereas the terminus was found at the opposite end.
00:51.1 our agriculture, and many aspects of our industry,
00:57.3 Now, bacteria are also the most abundant life form
01:35.2 there is a big difference between eukaryotic cells
02:58.2 just floating around with no spatial organization.
07:04.3 that is known as MreB, and so it's the same story.
11:55.2 that are important for other mechanical functions.
15:41.1 This protein accumulates at both ends of the cells
17:37.3 and you have a certain program of gene expression.
20:42.2 without being exposed to the extracellular milieu,
24:33.0 And then, if I randomly take this region, 1 and 2,
03:34.2 a few examples that I think illustrate the point.
06:08.2 and so it appears here as a pseudocolored yellow,
08:22.2 And when it elongates its width remains constant,
10:58.3 and become straight rods, as shown in this image,
11:12.1 but now you can... if you overproduce crescentin,
13:54.2 that, as you can see in this electron micrograph,
15:11.2 these are the proteins that sense the environment
25:41.3 by the fact that there has been a lot of advances
05:59.1 we're looking at FtsZ by fluorescence microscopy
09:06.3 because they don't have this elongation process.
10:27.0 and it's always the side of the inner curvature.
10:50.1 Okay, so, when the cells do not have crescentin,
13:02.2 I showed you MreB, which is the most famous one,
13:15.3 there are other bacterial cytoskeletal proteins,
13:18.0 and probably the most famous one is bactofilins,
15:00.1 accumulate at both ends of, here, E. coli cells,
18:00.0 now the regulator is going to be phosphorylated,
20:45.2 where it could be attacked by the immune system.
21:40.2 This is important for the cells for this reason,
22:31.1 and this is going to help the cells to determine
23:28.2 such that... so here the DNA is shown in blue...
00:44.2 and they have a tremendous impact on everything
05:28.1 that are shown here by fluorescence microscopy.
08:17.3 and this E. coli cell, in addition to dividing,
13:06.2 And then there's intermediate filament proteins
13:59.1 because it has a flagellum at one of the cells,
14:58.0 which is shown by fluorescence microscopy here,
16:07.0 and thereby tethering the duplicated chromosome
19:57.3 in green is actin and in red is the bacteria...
20:13.1 Now, at the back of the little bacterial cells,
21:09.3 but this protein also exists in other bacteria.
21:23.3 and so it accumulates on one side of the cells,
24:09.1 over 100 hundred locations along the chromosome
02:00.2 because there are membrane-enclosed organelles
04:21.0 of the bacterial protein, the tubulin homolog,
04:48.1 have evolved from a common bacterial ancestor.
07:39.1 it's going to form those really nice filaments
07:56.2 and these little patches are actually rotating
08:48.0 presumably because they are too fat, too wide,
10:37.0 so it means that it has this gentle curvature,
17:02.2 and in red you have a phosphatase accumulating
17:35.1 and therefore that regulator is phosphorylated
18:53.2 but they are expressed, or they are localized,
19:42.2 So, you're going to have actin-based motility.
19:54.2 and this is shown in this static image here...
20:56.0 which is important for a variety of functions.
22:22.2 the lowest concentration of the MinC inhibitor
23:38.1 that is predictable and conserved across cells
24:50.1 This is actually important because in bacteria
00:14.1 I am also a professor of molecular, cellular,
02:47.1 and complex spatial patterning as shown here.
03:06.2 there's been a big revolution in microbiology
05:18.3 is also going to form filamentous structures,
05:40.0 are going to arrange to form a ring structure
06:31.3 resulting in the formation of new cell walls.
07:02.0 Now, many bacteria also have an actin homolog
12:26.2 and what was shown by atomic force microscopy
15:17.3 and to swim away from things they don't like.
15:59.0 and PopZ is actually tethering the chromosome
16:33.0 And, in Caulobacter, it's going to produce...
18:33.2 is the pole localization of virulence factors
19:16.1 when this pathogen is in the eukaryotic cells
19:19.0 this protein, shown in red in this schematic,
19:46.2 And this is important for the bacterial cells
22:08.1 It does that by inhibiting the polymerization
23:12.2 but most of them have one circular chromosome
23:26.0 but it is folded in a very organized fashion,
24:27.1 was always found at the one end of the cells,
24:48.1 would be located in between inside the cells.
26:05.0 But there are also advances in microfluidics,
01:13.0 We cannot see them, they're invisible to us,
04:52.0 So, what this means is that during evolution
05:14.0 so, this is in vitro with purified proteins.
08:51.2 to allow the polymerization of the FtsZ ring
16:24.1 They can actually recognize one of the cells
24:03.2 Now, what was done in Caulobacter is that...
25:19.2 Okay, so I hope that I've convinced you that
00:32.3 and this sophisticated spatial organization
01:50.0 if you were imaging by electron microscopy.
02:07.2 The bacterial cell is, relatively speaking,
02:53.1 Bacteria cells were pictured, or perceived,
03:32.2 and so therefore I'm just going to describe
03:42.1 there are three major cytoskeletal systems:
06:37.1 So, what you can do by genetic engineering,
06:42.1 and this is what we did in this experiment,
12:29.2 is that those FilP filaments are important,
18:41.2 there is a protein called IcsA in Shigella,
21:25.2 the outline of the cells is shown in green,
25:28.1 of cellular function and cellular behavior,
25:38.2 and this is going to be greatly facilitated
26:15.0 so certainly it's going to be very exciting
02:29.3 But in addition, it's been known for years
07:44.3 MreB is also going to form short filaments
07:54.1 that appears here as those little patches,
09:24.1 and they all have this domain organization
09:33.2 and you also have a head and a tail domain
10:13.0 in the absence of cofactors or nucleotide.
12:14.1 So, FilP is found in Streptomyces species,
15:38.3 again, looking by fluorescence microscopy.
16:42.0 So, here is what we call the swarmer cell,
18:28.0 and it can play a very important function.
23:31.1 such that each gene is going to be located
24:43.2 and anything in between on the chromosome,
25:15.2 is going to be made also at that location.
03:08.2 with the realization that bacterial cells
03:15.1 So, for one, they do have a cytoskeleton,
04:38.1 Now, there is no question in the field...
05:03.0 Okay, so FtsZ, if you purify it in vitro,
07:42.0 and, inside the cell which is shown here,
11:14.2 so if the cells have too much crescentin,
11:18.3 you accentuate the curvature of the cells
11:50.2 but then there's other bacteria that have
11:53.1 other intermediate filament-like proteins
12:10.0 intermediate filament protein in bacteria
12:18.2 that form those very long cell filaments,
13:50.2 is a bacterium that is dear to the heart,
14:02.2 it has an appendage which we call a stalk
14:47.2 that accumulate at the ends of the cells,
17:48.1 is going to inherit only the phosphatase,
20:01.1 so, first of all, you can see the outline
22:04.1 is in fact an inhibitor of cell division.
22:42.3 which is right in the middle of the cells
23:20.2 by being condensed about a thousand-fold.
24:55.0 and, therefore, when transcription starts
25:25.0 that is really important for many aspects
01:18.2 unlike complex organisms like ourselves,
01:20.2 they're typically made of a single cell,
02:55.3 as tiny little bags full of biomolecules
04:08.1 is a very important protein in bacteria,
06:44.1 and what you're seeing here is now cells
06:47.0 that are growing in the absence of FtsZ.
08:35.1 that affects its polymerization process,
09:03.2 Spherical bacteria tend to not have MreB
09:56.0 as animal intermediate filament proteins
13:13.1 But what's more is that we now know that
13:38.1 The bacteria also exhibit cell polarity.
14:08.0 This appendage is basically an extension
15:03.2 but it has been shown also to accumulate
17:50.1 because of this asymmetric localization,
20:05.1 and you can see that the bacteria cells,
20:30.0 What you see is that the bacterial cell,
26:10.0 in, of course, cryo-electron microscopy,
26:35.1 who helped me produce some of the movies
01:09.0 And this is remarkable considering that
01:24.2 the bacterial cell itself is very small
02:12.1 So, it's made of a cytoplasmic membrane
02:42.2 to specific locations inside the cells,
04:06.1 So, FtsZ, as I'll show you in a minute,
04:54.1 the protein sequence has changed a lot,
06:49.1 Now, they can still elongate just fine,
07:30.2 of the MreB protofilaments and F-actin.
11:04.0 the curvature of Caulobacter crescentus
12:35.1 to the mechanical strength of the cell.
12:59.3 In bacteria, there is an actin homolog.
13:29.1 They are not found in eukaryotic cells.
17:44.0 immediately after cell division occurs,
18:17.2 Now, asymmetric localization of protein
18:48.1 and these proteins are surface-exposed,
21:28.1 but what's amazing as I start the movie
22:17.3 from one end of the cells to the other,
23:04.2 and that is mediated by the chromosome.
24:59.2 So, this is unlike in eukaryotic cells,
25:32.0 and it is clear that we are only seeing
26:23.2 I would like to acknowledge, of course,
02:27.0 So, in that respect, they are simpler.
03:01.3 Well, that turned out to be incorrect.
04:18.1 this is the crystal structure of FtsZ,
07:28.1 So, here you're seeing an atomic model
07:37.0 and incubate it in the presence of ATP
10:06.1 that look like intermediate filaments,
14:45.1 and that is because there are proteins
15:35.2 is this protein in red, which is PopZ,
16:48.2 because of the asymmetric localization
18:56.2 specifically on one side of the cells,
20:20.2 to move into the eukaryotic cytoplasm,
21:35.3 from one end of the cells to the other
25:08.0 since each gene is going to be located
26:37.2 that I presented in this presentation.
01:38.2 and bacterial cells in terms of size.
02:05.1 ER (endoplasmic reticulum) and Golgi.
03:38.0 So, starting with the cytoskeleton...
04:10.2 it's virtually found in all bacteria,
05:55.1 So, this is shown here in this movie.
07:23.1 the similarity between MreB and actin
07:59.2 across the circumference of the cell,
09:10.0 But there are some bacteria that also
09:53.1 It has similar biochemical properties
10:08.2 as shown here by electron microscopy,
10:10.2 and it does that without having to...
10:43.0 that forms the filamentous structure,
11:35.0 a big body of work that suggests that
11:46.2 Caulobacter crescentus has crescentin
13:57.1 exhibits a lot of cellular asymmetry,
16:15.1 Okay, so what I showed you previously
17:46.1 now you see one of the daughter cells
20:09.0 you can see how much smaller they are
20:11.0 in comparison to the eukaryotic cell.
22:15.2 So, because you have this oscillation
00:25.1 and in particular I would like to...
08:05.2 and so, thereby, cell wall synthesis
08:19.3 before dividing, it has to elongate.
08:41.2 such that now the cells are going to
09:12.1 have intermediate filament proteins.
09:31.1 that are separated by short linkers,
11:48.2 that's important for cell curvature,
14:16.3 so, increase the amount of membrane,
15:15.2 to swim towards things that the like
15:53.1 is that, in green, you have the DNA,
17:57.3 which has inherited only the kinase,
18:58.2 and this is shown in this schematic,
20:25.1 to escape from the eukaryotic cells,
20:27.1 and this is shown in this schematic.
03:53.1 Well, now we know that we can find,
06:24.1 is going to constrict, or condense,
07:10.1 MreB was discovered many years ago,
11:21.0 and now the cells look like bagels.
11:27.1 now the cells are going to filament
12:40.2 not mechanically as strong, as fit,
13:44.2 this cell polarity is actually seen
13:48.3 So, my favorite example, of course,
14:23.1 And actually, if you pay attention,
14:43.1 but is seen at the molecular level,
14:51.2 A prime example, the first example,
15:08.1 So, what chemoreceptors are is that
17:55.2 whereas in the other daughter cell,
19:22.1 is going to recruit the eukaryotic,
21:20.0 that has been fluorescently labeled
21:49.0 that I don't have time to describe,
24:24.1 such that the origin of replication
24:39.1 they would be located roughly here,
24:41.2 and 3 and 4 would be located there,
01:56.2 and, as you can see, the cytoplasm
02:02.2 such as the nucleus, mitochondria,
02:14.3 that is surrounded by a cell wall,
05:34.1 So, this is how it would look like
05:38.1 and this is because FtsZ filaments
08:33.0 so you can do this by adding drugs
09:36.0 that vary in size and in position.
10:56.2 now the cells lose their curvature
12:54.2 Alright, so, I gave you an example
14:38.1 cell polarity is actually not seen
18:08.0 and therefore different cell fate,
19:34.3 of actin on one side of the cells,
20:33.0 through this actin-based motility,
21:01.2 and this is really a nice example.
00:07.2 Hi. I'm Christine Jacobs-Wagner.
01:22.2 but also because they are very...
06:39.3 you can deplete the cell of FtsZ,
06:55.0 that are eventually going to die.
07:12.1 but at the protein sequence level
08:30.3 But if you inhibit MreB activity,
08:54.1 and therefore they cannot divide.
09:14.1 And so, here, what I'm showing is
12:21.1 and FilP here is shown in yellow,
13:25.1 in a variety of bacterial species
15:27.0 we talk about pole localizations.
17:05.1 at the opposite end of the cells.
17:08.2 Now, this phosphatase and kinase,
17:31.3 the phosphatase at the other end,
18:06.2 between those two daughter cells,
18:24.0 It can also been seen in bacteria
18:36.0 in Shigella and Listeria species.
18:39.0 So, in these two human pathogens,
20:23.0 but it's going to also allow them
20:53.3 of pole localization of proteins,
26:45.2 And thank you for your attention.
01:17.0 They are not only small because,
02:20.1 there is the DNA, the ribosomes,
02:22.0 the proteins, the metabolites...
02:40.1 in which molecules are localized
03:10.2 do exhibit spatial organization,
03:12.3 but only at the molecular level.
05:21.0 and these filamentous structures
06:19.3 from the top of from the bottom.
07:14.1 the similarity with actin was...
10:35.1 because it has a crescent shape,
13:27.1 and they are unique to bacteria.
14:33.2 So, a lot of cellular asymmetry.
15:13.2 and allow bacteria that can swim
15:20.1 There are many other examples of
16:40.0 that have a different cell fate.
16:50.3 of signal transduction proteins,
18:14.3 of signal transduction proteins.
22:33.1 where the middle of the cell is,
22:35.1 because, now, FtsZ ring assembly
22:37.3 is only going to be able to form
23:23.1 Alright, so it has to be folded,
06:06.2 the yellow fluorescent protein,
06:22.2 So, as the cells grow this FtsZ
11:33.1 And so, then, there is a lot...
15:48.1 One that is shown in this image
16:57.1 these are pre-divisional cells,
17:30.1 you have the kinase at one end,
22:20.1 it means that, on time average,
23:10.0 typically, they have one or two
24:36.2 on each side of the chromosome,
25:55.2 which is very important because
01:27.2 relative to most animal cells,
01:41.2 So, it you were to slice open,
02:24.1 all in one single compartment.
04:27.2 At the protein sequence level,
06:51.1 but they can no longer divide,
08:46.0 and then they're going to die,
10:23.2 just on one side of the cells,
12:12.1 that was well studied is FilP.
12:37.1 So, without FilP the cells are
12:43.2 and this is really reminiscent
14:05.2 at the other end of the cells.
19:03.0 where IcsA has been localized,
19:48.2 because now the bacterial cell
21:54.2 And therefore, MinC, together,
23:35.2 at a location inside the cells
23:51.1 So, in Caulobacter crescentus,
00:40.2 So, as you all probably know,
01:48.1 you will see a big difference
01:52.1 So, this is illustrated here.
03:04.1 Within the last decade or so,
03:40.2 so, we know that in our cells
03:44.3 microtubules made of tubulin,
03:47.0 microfilaments made of actin,
05:26.1 to form those beautiful rings
06:11.1 and now the FtsZ ring appears
08:27.1 and this is mediated by MreB.
14:49.2 which we call the cell poles.
15:06.0 at the ends of many bacteria.
16:30.3 which divides asymmetrically.
16:53.0 and an example is shown here.
17:11.0 which have opposing activity,
18:51.1 so they face the environment,
19:13.1 and this is important because
22:47.3 protein localization pattern.
23:42.1 at the same cell cycle stage.
24:21.2 follows a linear arrangement,
00:27.0 I hope you convince you that
01:15.1 because they are very small.
03:24.2 including cell polarization,
04:15.2 As shown in this image here,
05:42.1 which we call the FtsZ ring,
08:15.1 So, this is an E. coli cell,
20:51.1 So, those are a few examples
21:13.1 What you see here is, again,
21:18.2 in white is the MinD protein
21:22.0 so that we can visualize it,
21:57.0 by being complexed with MinD
22:10.2 of the FtsZ tubulin homolog.
22:45.1 because of this very dynamic
23:15.2 that is going to be packaged
24:53.1 there is no nuclear envelope
04:57.2 but at the structural level
04:59.3 it has changed not as much.
07:20.0 but at the structural level
12:57.2 of a tubulin homolog, FtsZ.
13:46.3 at the morphological level.
14:40.2 at the morphological level,
18:31.1 One of my favorite examples
20:07.1 those tiny little red dots,
22:27.0 of FtsZ ring polymerization
24:57.1 translation starts as well.
03:18.2 actually they invented it,
04:40.2 it is widely accepted that
05:16.2 But, inside of cells, FtsZ
05:53.0 so, for dividing the cell.
10:31.1 So, Caulobacter crescentus
11:01.2 and it has been shown that
12:05.2 And so, another example of
17:33.2 and the kinase is winning,
18:25.3 that divide symmetrically,
20:15.2 you see those actin tails.
21:16.1 fluorescence microscopy...
21:33.3 So, the protein oscillates
22:29.1 is actually in the middle,
24:06.1 what is shown here is that
26:40.1 And of course a big thanks
00:16.0 and developmental biology
05:11.3 So, this is shown here...
05:47.1 and the reason is because
08:02.1 and they are in a complex
09:22.1 vimentin, keratin, lamin,
14:28.2 producing a daughter cell
16:44.0 and then the stalk cells.
17:41.3 But when division occurs,
23:18.2 inside the bacterial cell
01:05.0 any life, on this Earth.
01:11.2 we cannot even see them.
02:45.0 exhibiting cell polarity
11:16.3 then what happens now...
14:19.1 and increasing, thereby,
16:46.2 This is in part mediated
00:42.3 bacteria are everywhere
03:54.3 in the bacterial world,
08:04.1 with cell wall enzymes,
10:33.1 got its name crescentus
11:44.0 Now, Caulobacter has...
12:33.0 or at least contribute,
13:52.3 Caulobacter crescentus,
16:01.1 at the end of the cells
20:03.1 of the eukaryotic cells
23:03.0 in the bacterial cells,
25:34.0 the tip of the iceberg,
26:12.2 such as cryotomography,
06:14.1 as a band or two dots,
07:34.2 So, if you purify MreB
08:25.2 and this is important,
13:41.2 Now, in some bacteria,
14:36.0 But, in most bacteria,
17:16.3 so the same substrate,
22:02.1 Now, this MinC protein
25:05.2 And so, it means that,
00:20.3 In this presentation,
06:29.1 along the cell width,
12:00.1 that are in our cells
13:05.0 but there are others.
14:11.2 of the cell envelope.
18:45.3 and ActA in Listeria,
23:07.3 Okay, so, bacteria...
01:59.0 is compartmentalized
07:51.3 along the cell body,
11:22.2 And now, if for fun,
14:56.1 Now, chemoreceptors,
00:12.2 at Yale University.
00:46.2 that we care about,
02:09.1 is far more simple.
05:57.1 In this movie, now,
07:26.2 is really striking.
10:44.3 here shown in pink,
13:31.0 So, as you can see,
14:21.2 nutrient transport.
19:25.0 so the host, actin,
21:38.1 in tens of seconds.
26:21.1 So, to just finish,
14:54.0 is chemoreceptors.
18:04.2 of gene expression
19:05.2 shown in Shigella,
26:07.2 in image analysis,
16:12.0 at opposite ends.
16:55.0 So, here you see,
09:19.2 so, for example,
24:46.1 chromosomal map,
01:46.2 like our cells,
05:36.1 in a schematic,
07:08.2 Just like FtsZ,
16:26.2 from the other.
01:00.2 on this planet
09:44.3 is crescentin.
04:04.1 This is FtsZ.
00:38.2 of the cell.
13:35.1 in bacteria.
21:42.3 because MinD
22:51.1 Alright, so,
19:41.0 to move.

Part 2: DNA Segregation and Active Intracellular Transport in Bacteria

10:02.2 it's going to spontaneously self-assemble into those beautiful filaments
26:42.0 to the funding agencies that support research in bacterial cell biology.
08:37.1 now the cells still grow, but now cell wall synthesis is disorganized
24:14.3 and it was shown that the arrangement of those genes inside the cells
25:48.1 So, starting with single-molecule fluorescence microscopy techniques,
25:58.3 this is increasing the spatial resolution at which we can see things,
06:52.3 and therefore now those cells are going to form those long filaments
16:36.2 Caulobacter, when it divides, is going to produce two daughter cells
19:51.1 is going to be able to move in the cytoplasm of the eukaryotic cell,
00:29.0 the spatial organization of bacterial cells is remarkably complex,
01:39.0 But there is another difference in terms of cellular organization.
03:49.0 and intermediate filaments made of intermediate filament proteins.
14:13.2 This is going to increase the surface-to-volume ratio of the cell,
16:59.1 and in blue you have a kinase accumulating at one end of the cells
26:02.1 and for bacterial cells that are very tiny this is very important.
06:16.1 and the reason is because it's as if you were looking at the ring
10:16.0 Now, inside of cells, crescentin is also going to form filaments,
10:20.2 and what's really neat is that it's going to form those filaments
11:57.2 And this is reminiscent to all the intermediate filament proteins
15:29.1 So, there is a lot of protein at the pole with pole localization.
15:55.2 so those are the chromosomes, the chromosome has been duplicated,
11:29.2 into those tightly-coiled cells that look like a telephone cord.
19:31.2 Okay, so we're going to have polymerization and depolymerization
21:58.2 is basically oscillating from one end of the cells to the other.
25:44.2 in microscopy and microscopy-related techniques in recent years.
04:23.2 and here are the crystal structures of the eukaryotic tubulins.
05:44.0 and they're going to specifically form at the site of division,
05:49.2 this ring is going to be important for the cytokinesis process,
22:40.2 where there is the lowest concentration of that MinC inhibitor,
04:33.3 At the structural level, there is really beautiful similarity.
05:07.3 it's going to polymerize if you put it in the presence of GTP.
09:41.2 the first intermediate filament-like protein found in bacteria
12:46.2 to our intermediate filaments in our cells, in our skin cells,
12:50.1 that are important for the mechanical strength of those cells.
08:11.0 and this is going to be important for the elongation process.
20:35.1 is going to be able to move into another, a neighboring cell,
21:03.3 This is the localization of a protein called MinD in E. coli,
25:35.3 and so there are many discoveries that still have to be made,
09:00.1 in particular the rod-shaped bacteria that have to elongate.
09:58.1 and a striking one is that if you purify crescentin in vitro
11:24.3 you overproduce crescentin and you also block cell division,
13:32.3 there is really a richness in terms of cytoskeletal elements
15:43.3 and it's going to achieve a lot of polarized function there.
16:28.1 And so, this is an example, again in Caulobacter crescentus,
23:56.0 and it has a typical circular chromosome like many bacteria,
00:18.0 and an investigator of the Howard Hughes Medical Institute.
00:22.3 I would like to tell you about the cell biology of bacteria
01:32.2 and so we have a big difference between eukaryotic cells...
08:07.3 is going to be guided along the circumference of the cells,
09:16.3 intermediate filament proteins that are found in our cells,
12:02.0 that are also important for different mechanical functions.
12:23.1 and it forms those filamentous structures inside the cells,
13:09.1 that are important for a variety of cytoskeletal functions.
17:14.0 actually they have opposing activity on the same regulator,
19:09.1 So, you can see that it accumulates at one end of the cell,
02:17.0 and then inside the cytoplasm is pretty much everything...
07:16.2 there is some similarity but it's not incredibly apparent,
09:27.1 made of four coil-coiled-forming segments, shown in green,
10:46.2 on one side of the cells, the side of the inner curvature.
14:31.2 that is a little bit shorter than the other daughter cell.
21:51.1 but it's also associated with another protein called MinC.
24:11.2 were localized inside of cells by fluorescence microscopy,
25:02.2 where transcription and translation are separated in time.
06:26.0 and that's going to promote cell wall synthesis across...
08:43.1 get fatter and fatter and fatter until they became round,
11:09.1 So, this is what happened when you don't have crescentin,
11:40.1 is by mechanically affecting the way that the cells grow.
15:32.1 Another example, which is here in Caulobacter crescentus,
16:03.1 because it can interact indirectly with the DNA sequence,
16:21.1 but there are also proteins that can do better than that.
17:26.2 Now, in the mother cells, so in the pre-divisional cells,
19:37.0 and this is going to allow to cells, the bacterial cells,
20:59.1 Now, those patterns can be even more intricate than that,
23:46.3 I'm going to show you the case of Caulobacter crescentus.
26:28.3 I would like to thank past and current members of my lab.
00:48.2 so, starting with our health, also with our environment,
02:49.3 Well, this was thought to be unique to eukaryotic cells.
03:57.1 counterparts to all three types of cytoskeletal systems.
10:40.0 and this is actually mediated by this protein crescentin
17:18.2 and this regulator, whether it is phosphorylated or not,
17:21.1 it's going to be able to turn on gene expression or not.
20:39.1 and thereby it's going to be able to colonize the tissue
22:53.2 I've shown you that bacteria have cytoskeletal elements,
23:59.2 with a single origin and a terminus at the opposite end.
25:52.0 and super-resolution fluorescence microscopy techniques,
02:31.3 that the eukaryotic cell has an elaborate cytoskeleton,
02:37.2 and also they can have sophisticated spatial patterning
11:37.2 the way that crescentin filaments affect cell curvature
13:21.1 and these also are important for cytoskeletal functions
16:18.0 are proteins that accumulate at both ends of the cells,
19:27.1 and by doing so it's going to create those actin tails.
22:56.2 they also exhibit spatial patterning and cell polarity,
23:44.0 Okay, so, this has been shown in many bacterial models.
25:10.1 at a predictable and conserved region inside the cells,
26:32.0 In particular, I would like to thank Jennifer Heinritz,
01:02.1 and they are absolutely essential for sustaining life,
03:21.1 and also they can exhibit intricate spatial patterning
04:30.2 there is similarity, but it's not incredibly striking.
04:43.2 the bacterial FtsZ protein and the eukaryotic tubulins
06:01.2 because FtsZ has been tagged by a fluorescent protein,
11:06.1 is important for surface adhesion in natural habitats.
17:52.2 and now the regulator is going to be unphosphorylated,
18:02.2 and therefore you're going to have a different program
19:07.1 but you would see the same thing for ActA in Listeria.
21:30.2 is that you can see this localization is very dynamic.
25:13.0 it means that the protein that is encoded by that gene
00:09.2 I am the director of the Microbial Sciences Institute
00:54.2 and so it is very important for us to study bacteria.
04:00.1 So, let's start with the tubulin homolog in bacteria.
06:57.2 So, many bacteria have a tubulin homolog called FtsZ.
09:39.0 Now, the first bacteria to make a filament protein...
09:47.0 Now, this protein was bound in Caulobacter crescentus
10:53.2 so if we delete the genes that encode for crescentin,
12:16.2 and here this is shown is Streptomyces pseudocolored,
14:25.1 division is also asymmetric, unequal, in Caulobacter,
18:20.1 is not only seen in asymmetrically-dividing bacteria.
21:46.2 oscillates through a very simple biochemical reaction
25:22.0 bacteria exhibit a sophisticated spatial organization
26:25.2 all the bacterial cell biology labs across the world.
01:43.2 through a bacterial cell and through an animal cell,
01:53.3 So, in the bottom you have a typical eukaryotic cell
04:12.2 because it's absolutely essential for cell division.
08:57.1 So, you have... some bacteria have an actin homolog,
09:49.1 and, again, it has the same structural organization.
18:10.1 because of this asymmetric localization of proteins,
20:18.0 Well, this is what's going to promote those bacteria
23:00.2 but there is another element of spatial organization
23:53.2 so, this is the chromosome of Caulobacter crescentus
26:17.2 to study the cell biology of bacteria in the future.
00:35.0 is very important for the behavior and the function
03:27.2 so, there's been a lot of evidence in recent years.
03:30.1 I won't have time to describe all of this evidence,
05:23.0 are going to associate underneath the cell membrane
05:30.1 So, this is looking at a cross-section of the cell.
07:48.1 that are going to be just beneath the cell membrane
15:24.0 proteins that accumulate at the end of the cells...
19:00.2 and this is shown in this electron micrograph here,
24:29.3 whereas the terminus was found at the opposite end.
00:51.1 our agriculture, and many aspects of our industry,
00:57.3 Now, bacteria are also the most abundant life form
01:35.2 there is a big difference between eukaryotic cells
02:58.2 just floating around with no spatial organization.
07:04.3 that is known as MreB, and so it's the same story.
11:55.2 that are important for other mechanical functions.
15:41.1 This protein accumulates at both ends of the cells
17:37.3 and you have a certain program of gene expression.
20:42.2 without being exposed to the extracellular milieu,
24:33.0 And then, if I randomly take this region, 1 and 2,
03:34.2 a few examples that I think illustrate the point.
06:08.2 and so it appears here as a pseudocolored yellow,
08:22.2 And when it elongates its width remains constant,
10:58.3 and become straight rods, as shown in this image,
11:12.1 but now you can... if you overproduce crescentin,
13:54.2 that, as you can see in this electron micrograph,
15:11.2 these are the proteins that sense the environment
25:41.3 by the fact that there has been a lot of advances
05:59.1 we're looking at FtsZ by fluorescence microscopy
09:06.3 because they don't have this elongation process.
10:27.0 and it's always the side of the inner curvature.
10:50.1 Okay, so, when the cells do not have crescentin,
13:02.2 I showed you MreB, which is the most famous one,
13:15.3 there are other bacterial cytoskeletal proteins,
13:18.0 and probably the most famous one is bactofilins,
15:00.1 accumulate at both ends of, here, E. coli cells,
18:00.0 now the regulator is going to be phosphorylated,
20:45.2 where it could be attacked by the immune system.
21:40.2 This is important for the cells for this reason,
22:31.1 and this is going to help the cells to determine
23:28.2 such that... so here the DNA is shown in blue...
00:44.2 and they have a tremendous impact on everything
05:28.1 that are shown here by fluorescence microscopy.
08:17.3 and this E. coli cell, in addition to dividing,
13:06.2 And then there's intermediate filament proteins
13:59.1 because it has a flagellum at one of the cells,
14:58.0 which is shown by fluorescence microscopy here,
16:07.0 and thereby tethering the duplicated chromosome
19:57.3 in green is actin and in red is the bacteria...
20:13.1 Now, at the back of the little bacterial cells,
21:09.3 but this protein also exists in other bacteria.
21:23.3 and so it accumulates on one side of the cells,
24:09.1 over 100 hundred locations along the chromosome
02:00.2 because there are membrane-enclosed organelles
04:21.0 of the bacterial protein, the tubulin homolog,
04:48.1 have evolved from a common bacterial ancestor.
07:39.1 it's going to form those really nice filaments
07:56.2 and these little patches are actually rotating
08:48.0 presumably because they are too fat, too wide,
10:37.0 so it means that it has this gentle curvature,
17:02.2 and in red you have a phosphatase accumulating
17:35.1 and therefore that regulator is phosphorylated
18:53.2 but they are expressed, or they are localized,
19:42.2 So, you're going to have actin-based motility.
19:54.2 and this is shown in this static image here...
20:56.0 which is important for a variety of functions.
22:22.2 the lowest concentration of the MinC inhibitor
23:38.1 that is predictable and conserved across cells
24:50.1 This is actually important because in bacteria
00:14.1 I am also a professor of molecular, cellular,
02:47.1 and complex spatial patterning as shown here.
03:06.2 there's been a big revolution in microbiology
05:18.3 is also going to form filamentous structures,
05:40.0 are going to arrange to form a ring structure
06:31.3 resulting in the formation of new cell walls.
07:02.0 Now, many bacteria also have an actin homolog
12:26.2 and what was shown by atomic force microscopy
15:17.3 and to swim away from things they don't like.
15:59.0 and PopZ is actually tethering the chromosome
16:33.0 And, in Caulobacter, it's going to produce...
18:33.2 is the pole localization of virulence factors
19:16.1 when this pathogen is in the eukaryotic cells
19:19.0 this protein, shown in red in this schematic,
19:46.2 And this is important for the bacterial cells
22:08.1 It does that by inhibiting the polymerization
23:12.2 but most of them have one circular chromosome
23:26.0 but it is folded in a very organized fashion,
24:27.1 was always found at the one end of the cells,
24:48.1 would be located in between inside the cells.
26:05.0 But there are also advances in microfluidics,
01:13.0 We cannot see them, they're invisible to us,
04:52.0 So, what this means is that during evolution
05:14.0 so, this is in vitro with purified proteins.
08:51.2 to allow the polymerization of the FtsZ ring
16:24.1 They can actually recognize one of the cells
24:03.2 Now, what was done in Caulobacter is that...
25:19.2 Okay, so I hope that I've convinced you that
00:32.3 and this sophisticated spatial organization
01:50.0 if you were imaging by electron microscopy.
02:07.2 The bacterial cell is, relatively speaking,
02:53.1 Bacteria cells were pictured, or perceived,
03:32.2 and so therefore I'm just going to describe
03:42.1 there are three major cytoskeletal systems:
06:37.1 So, what you can do by genetic engineering,
06:42.1 and this is what we did in this experiment,
12:29.2 is that those FilP filaments are important,
18:41.2 there is a protein called IcsA in Shigella,
21:25.2 the outline of the cells is shown in green,
25:28.1 of cellular function and cellular behavior,
25:38.2 and this is going to be greatly facilitated
26:15.0 so certainly it's going to be very exciting
02:29.3 But in addition, it's been known for years
07:44.3 MreB is also going to form short filaments
07:54.1 that appears here as those little patches,
09:24.1 and they all have this domain organization
09:33.2 and you also have a head and a tail domain
10:13.0 in the absence of cofactors or nucleotide.
12:14.1 So, FilP is found in Streptomyces species,
15:38.3 again, looking by fluorescence microscopy.
16:42.0 So, here is what we call the swarmer cell,
18:28.0 and it can play a very important function.
23:31.1 such that each gene is going to be located
24:43.2 and anything in between on the chromosome,
25:15.2 is going to be made also at that location.
03:08.2 with the realization that bacterial cells
03:15.1 So, for one, they do have a cytoskeleton,
04:38.1 Now, there is no question in the field...
05:03.0 Okay, so FtsZ, if you purify it in vitro,
07:42.0 and, inside the cell which is shown here,
11:14.2 so if the cells have too much crescentin,
11:18.3 you accentuate the curvature of the cells
11:50.2 but then there's other bacteria that have
11:53.1 other intermediate filament-like proteins
12:10.0 intermediate filament protein in bacteria
12:18.2 that form those very long cell filaments,
13:50.2 is a bacterium that is dear to the heart,
14:02.2 it has an appendage which we call a stalk
14:47.2 that accumulate at the ends of the cells,
17:48.1 is going to inherit only the phosphatase,
20:01.1 so, first of all, you can see the outline
22:04.1 is in fact an inhibitor of cell division.
22:42.3 which is right in the middle of the cells
23:20.2 by being condensed about a thousand-fold.
24:55.0 and, therefore, when transcription starts
25:25.0 that is really important for many aspects
01:18.2 unlike complex organisms like ourselves,
01:20.2 they're typically made of a single cell,
02:55.3 as tiny little bags full of biomolecules
04:08.1 is a very important protein in bacteria,
06:44.1 and what you're seeing here is now cells
06:47.0 that are growing in the absence of FtsZ.
08:35.1 that affects its polymerization process,
09:03.2 Spherical bacteria tend to not have MreB
09:56.0 as animal intermediate filament proteins
13:13.1 But what's more is that we now know that
13:38.1 The bacteria also exhibit cell polarity.
14:08.0 This appendage is basically an extension
15:03.2 but it has been shown also to accumulate
17:50.1 because of this asymmetric localization,
20:05.1 and you can see that the bacteria cells,
20:30.0 What you see is that the bacterial cell,
26:10.0 in, of course, cryo-electron microscopy,
26:35.1 who helped me produce some of the movies
01:09.0 And this is remarkable considering that
01:24.2 the bacterial cell itself is very small
02:12.1 So, it's made of a cytoplasmic membrane
02:42.2 to specific locations inside the cells,
04:06.1 So, FtsZ, as I'll show you in a minute,
04:54.1 the protein sequence has changed a lot,
06:49.1 Now, they can still elongate just fine,
07:30.2 of the MreB protofilaments and F-actin.
11:04.0 the curvature of Caulobacter crescentus
12:35.1 to the mechanical strength of the cell.
12:59.3 In bacteria, there is an actin homolog.
13:29.1 They are not found in eukaryotic cells.
17:44.0 immediately after cell division occurs,
18:17.2 Now, asymmetric localization of protein
18:48.1 and these proteins are surface-exposed,
21:28.1 but what's amazing as I start the movie
22:17.3 from one end of the cells to the other,
23:04.2 and that is mediated by the chromosome.
24:59.2 So, this is unlike in eukaryotic cells,
25:32.0 and it is clear that we are only seeing
26:23.2 I would like to acknowledge, of course,
02:27.0 So, in that respect, they are simpler.
03:01.3 Well, that turned out to be incorrect.
04:18.1 this is the crystal structure of FtsZ,
07:28.1 So, here you're seeing an atomic model
07:37.0 and incubate it in the presence of ATP
10:06.1 that look like intermediate filaments,
14:45.1 and that is because there are proteins
15:35.2 is this protein in red, which is PopZ,
16:48.2 because of the asymmetric localization
18:56.2 specifically on one side of the cells,
20:20.2 to move into the eukaryotic cytoplasm,
21:35.3 from one end of the cells to the other
25:08.0 since each gene is going to be located
26:37.2 that I presented in this presentation.
01:38.2 and bacterial cells in terms of size.
02:05.1 ER (endoplasmic reticulum) and Golgi.
03:38.0 So, starting with the cytoskeleton...
04:10.2 it's virtually found in all bacteria,
05:55.1 So, this is shown here in this movie.
07:23.1 the similarity between MreB and actin
07:59.2 across the circumference of the cell,
09:10.0 But there are some bacteria that also
09:53.1 It has similar biochemical properties
10:08.2 as shown here by electron microscopy,
10:10.2 and it does that without having to...
10:43.0 that forms the filamentous structure,
11:35.0 a big body of work that suggests that
11:46.2 Caulobacter crescentus has crescentin
13:57.1 exhibits a lot of cellular asymmetry,
16:15.1 Okay, so what I showed you previously
17:46.1 now you see one of the daughter cells
20:09.0 you can see how much smaller they are
20:11.0 in comparison to the eukaryotic cell.
22:15.2 So, because you have this oscillation
00:25.1 and in particular I would like to...
08:05.2 and so, thereby, cell wall synthesis
08:19.3 before dividing, it has to elongate.
08:41.2 such that now the cells are going to
09:12.1 have intermediate filament proteins.
09:31.1 that are separated by short linkers,
11:48.2 that's important for cell curvature,
14:16.3 so, increase the amount of membrane,
15:15.2 to swim towards things that the like
15:53.1 is that, in green, you have the DNA,
17:57.3 which has inherited only the kinase,
18:58.2 and this is shown in this schematic,
20:25.1 to escape from the eukaryotic cells,
20:27.1 and this is shown in this schematic.
03:53.1 Well, now we know that we can find,
06:24.1 is going to constrict, or condense,
07:10.1 MreB was discovered many years ago,
11:21.0 and now the cells look like bagels.
11:27.1 now the cells are going to filament
12:40.2 not mechanically as strong, as fit,
13:44.2 this cell polarity is actually seen
13:48.3 So, my favorite example, of course,
14:23.1 And actually, if you pay attention,
14:43.1 but is seen at the molecular level,
14:51.2 A prime example, the first example,
15:08.1 So, what chemoreceptors are is that
17:55.2 whereas in the other daughter cell,
19:22.1 is going to recruit the eukaryotic,
21:20.0 that has been fluorescently labeled
21:49.0 that I don't have time to describe,
24:24.1 such that the origin of replication
24:39.1 they would be located roughly here,
24:41.2 and 3 and 4 would be located there,
01:56.2 and, as you can see, the cytoplasm
02:02.2 such as the nucleus, mitochondria,
02:14.3 that is surrounded by a cell wall,
05:34.1 So, this is how it would look like
05:38.1 and this is because FtsZ filaments
08:33.0 so you can do this by adding drugs
09:36.0 that vary in size and in position.
10:56.2 now the cells lose their curvature
12:54.2 Alright, so, I gave you an example
14:38.1 cell polarity is actually not seen
18:08.0 and therefore different cell fate,
19:34.3 of actin on one side of the cells,
20:33.0 through this actin-based motility,
21:01.2 and this is really a nice example.
00:07.2 Hi. I'm Christine Jacobs-Wagner.
01:22.2 but also because they are very...
06:39.3 you can deplete the cell of FtsZ,
06:55.0 that are eventually going to die.
07:12.1 but at the protein sequence level
08:30.3 But if you inhibit MreB activity,
08:54.1 and therefore they cannot divide.
09:14.1 And so, here, what I'm showing is
12:21.1 and FilP here is shown in yellow,
13:25.1 in a variety of bacterial species
15:27.0 we talk about pole localizations.
17:05.1 at the opposite end of the cells.
17:08.2 Now, this phosphatase and kinase,
17:31.3 the phosphatase at the other end,
18:06.2 between those two daughter cells,
18:24.0 It can also been seen in bacteria
18:36.0 in Shigella and Listeria species.
18:39.0 So, in these two human pathogens,
20:23.0 but it's going to also allow them
20:53.3 of pole localization of proteins,
26:45.2 And thank you for your attention.
01:17.0 They are not only small because,
02:20.1 there is the DNA, the ribosomes,
02:22.0 the proteins, the metabolites...
02:40.1 in which molecules are localized
03:10.2 do exhibit spatial organization,
03:12.3 but only at the molecular level.
05:21.0 and these filamentous structures
06:19.3 from the top of from the bottom.
07:14.1 the similarity with actin was...
10:35.1 because it has a crescent shape,
13:27.1 and they are unique to bacteria.
14:33.2 So, a lot of cellular asymmetry.
15:13.2 and allow bacteria that can swim
15:20.1 There are many other examples of
16:40.0 that have a different cell fate.
16:50.3 of signal transduction proteins,
18:14.3 of signal transduction proteins.
22:33.1 where the middle of the cell is,
22:35.1 because, now, FtsZ ring assembly
22:37.3 is only going to be able to form
23:23.1 Alright, so it has to be folded,
06:06.2 the yellow fluorescent protein,
06:22.2 So, as the cells grow this FtsZ
11:33.1 And so, then, there is a lot...
15:48.1 One that is shown in this image
16:57.1 these are pre-divisional cells,
17:30.1 you have the kinase at one end,
22:20.1 it means that, on time average,
23:10.0 typically, they have one or two
24:36.2 on each side of the chromosome,
25:55.2 which is very important because
01:27.2 relative to most animal cells,
01:41.2 So, it you were to slice open,
02:24.1 all in one single compartment.
04:27.2 At the protein sequence level,
06:51.1 but they can no longer divide,
08:46.0 and then they're going to die,
10:23.2 just on one side of the cells,
12:12.1 that was well studied is FilP.
12:37.1 So, without FilP the cells are
12:43.2 and this is really reminiscent
14:05.2 at the other end of the cells.
19:03.0 where IcsA has been localized,
19:48.2 because now the bacterial cell
21:54.2 And therefore, MinC, together,
23:35.2 at a location inside the cells
23:51.1 So, in Caulobacter crescentus,
00:40.2 So, as you all probably know,
01:48.1 you will see a big difference
01:52.1 So, this is illustrated here.
03:04.1 Within the last decade or so,
03:40.2 so, we know that in our cells
03:44.3 microtubules made of tubulin,
03:47.0 microfilaments made of actin,
05:26.1 to form those beautiful rings
06:11.1 and now the FtsZ ring appears
08:27.1 and this is mediated by MreB.
14:49.2 which we call the cell poles.
15:06.0 at the ends of many bacteria.
16:30.3 which divides asymmetrically.
16:53.0 and an example is shown here.
17:11.0 which have opposing activity,
18:51.1 so they face the environment,
19:13.1 and this is important because
22:47.3 protein localization pattern.
23:42.1 at the same cell cycle stage.
24:21.2 follows a linear arrangement,
00:27.0 I hope you convince you that
01:15.1 because they are very small.
03:24.2 including cell polarization,
04:15.2 As shown in this image here,
05:42.1 which we call the FtsZ ring,
08:15.1 So, this is an E. coli cell,
20:51.1 So, those are a few examples
21:13.1 What you see here is, again,
21:18.2 in white is the MinD protein
21:22.0 so that we can visualize it,
21:57.0 by being complexed with MinD
22:10.2 of the FtsZ tubulin homolog.
22:45.1 because of this very dynamic
23:15.2 that is going to be packaged
24:53.1 there is no nuclear envelope
04:57.2 but at the structural level
04:59.3 it has changed not as much.
07:20.0 but at the structural level
12:57.2 of a tubulin homolog, FtsZ.
13:46.3 at the morphological level.
14:40.2 at the morphological level,
18:31.1 One of my favorite examples
20:07.1 those tiny little red dots,
22:27.0 of FtsZ ring polymerization
24:57.1 translation starts as well.
03:18.2 actually they invented it,
04:40.2 it is widely accepted that
05:16.2 But, inside of cells, FtsZ
05:53.0 so, for dividing the cell.
10:31.1 So, Caulobacter crescentus
11:01.2 and it has been shown that
12:05.2 And so, another example of
17:33.2 and the kinase is winning,
18:25.3 that divide symmetrically,
20:15.2 you see those actin tails.
21:16.1 fluorescence microscopy...
21:33.3 So, the protein oscillates
22:29.1 is actually in the middle,
24:06.1 what is shown here is that
26:40.1 And of course a big thanks
00:16.0 and developmental biology
05:11.3 So, this is shown here...
05:47.1 and the reason is because
08:02.1 and they are in a complex
09:22.1 vimentin, keratin, lamin,
14:28.2 producing a daughter cell
16:44.0 and then the stalk cells.
17:41.3 But when division occurs,
23:18.2 inside the bacterial cell
01:05.0 any life, on this Earth.
01:11.2 we cannot even see them.
02:45.0 exhibiting cell polarity
11:16.3 then what happens now...
14:19.1 and increasing, thereby,
16:46.2 This is in part mediated
00:42.3 bacteria are everywhere
03:54.3 in the bacterial world,
08:04.1 with cell wall enzymes,
10:33.1 got its name crescentus
11:44.0 Now, Caulobacter has...
12:33.0 or at least contribute,
13:52.3 Caulobacter crescentus,
16:01.1 at the end of the cells
20:03.1 of the eukaryotic cells
23:03.0 in the bacterial cells,
25:34.0 the tip of the iceberg,
26:12.2 such as cryotomography,
06:14.1 as a band or two dots,
07:34.2 So, if you purify MreB
08:25.2 and this is important,
13:41.2 Now, in some bacteria,
14:36.0 But, in most bacteria,
17:16.3 so the same substrate,
22:02.1 Now, this MinC protein
25:05.2 And so, it means that,
00:20.3 In this presentation,
06:29.1 along the cell width,
12:00.1 that are in our cells
13:05.0 but there are others.
14:11.2 of the cell envelope.
18:45.3 and ActA in Listeria,
23:07.3 Okay, so, bacteria...
01:59.0 is compartmentalized
07:51.3 along the cell body,
11:22.2 And now, if for fun,
14:56.1 Now, chemoreceptors,
00:12.2 at Yale University.
00:46.2 that we care about,
02:09.1 is far more simple.
05:57.1 In this movie, now,
07:26.2 is really striking.
10:44.3 here shown in pink,
13:31.0 So, as you can see,
14:21.2 nutrient transport.
19:25.0 so the host, actin,
21:38.1 in tens of seconds.
26:21.1 So, to just finish,
14:54.0 is chemoreceptors.
18:04.2 of gene expression
19:05.2 shown in Shigella,
26:07.2 in image analysis,
16:12.0 at opposite ends.
16:55.0 So, here you see,
09:19.2 so, for example,
24:46.1 chromosomal map,
01:46.2 like our cells,
05:36.1 in a schematic,
07:08.2 Just like FtsZ,
16:26.2 from the other.
01:00.2 on this planet
09:44.3 is crescentin.
04:04.1 This is FtsZ.
00:38.2 of the cell.
13:35.1 in bacteria.
21:42.3 because MinD
22:51.1 Alright, so,
19:41.0 to move.

Videos in this Talk

Part 1: The critical role of spatial organization in bacterial cell function
Audience:
- Researcher
- Educators of Adv. Undergrad / Grad
Part 2: DNA Segregation and Active Intracellular Transport in Bacteria
Audience:
- Researcher
- Educators of Adv. Undergrad / Grad

Speaker: Christine Jacobs-Wagner

Total Duration: 0:59:39

Recorded: December 2014

All Talks in Microbiology

Talk Overview

Most bacterial cells are many, many times smaller than eukaryotic cells. Since they have no membrane-bound internal organelles, their cellular organization also appears much simpler. Over the last decade, however, scientists have come to understand that that bacterial cells have a cytoskeleton. Jacobs-Wagner explains that bacterial homologues of tubulin (FtsZ) and actin (MreB) are critical for cell division amongst other functions. Crescentin, a bacterial counterpart of intermediate filament proteins, gives Caulobacter crescentus its crescent shape. In addition, bacteria exhibit sophisticated spatial organization; proteins can be spatially patterned and the bacterial chromosome forms an organized structure that locates genes at specific positions in the cell.

In her second lecture, Jacobs-Wagner tells us about research in her lab into how bacterial chromosomal DNA is segregated. For distances as small as those found in a bacterial cell, diffusion can successfully distribute high copy number molecules throughout the cell. However, diffusion cannot effectively separate 2 chromosomes such that after cell division each daughter cell is likely to have one chromosome. To do this job, bacteria have evolved a partitioning system called ParABS. Jacobs-Wagner describes the how the ParABS system works to separate chromosomal DNA in C. crescentus.

Speaker Bio

Christine Jacobs-Wagner

Christine Jacobs-wagner

Christine Jacobs-Wagner received her BS in biochemistry from the University of Liège in Belgium and her PhD from the University of Liège and the Karolinska Institute. As a post-doctoral fellow she worked with Lucy Shapiro at Stanford University. In 2001, Jacobs-Wagner moved to Yale University where she is currently a Professor of Molecular, Cellular and… Continue Reading

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