Dimensional rearrangement of rod-shaped bacteria following nutritional shift-up. II. Experiments with Escherichia coli

Woldringh, Conrad L.; Grover, N.B.; Rosenberger, R. F.; Zaritsky, Arieh

doi:10.1016/0022-5193(80)90344-6

Cited by 61 publications

(66 citation statements)

References 25 publications

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“…E. coli regulates cell size in response to the availability of nutrients so that it grows larger in rich medium than in minimal medium (1,2,5). Because FA biosynthesis is altered in response to nutrient levels (56-58), we wondered whether the loss of FabH would interfere with the ability of E. coli to regulate cell size in response to nutrient availability.…”

Section: Loss Of Fabh Function Compromises Regulation Of Cell Size Inmentioning

confidence: 99%

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Regulation of cell size in response to nutrient availability by fatty acid biosynthesis in Escherichia coli

Yao

Davis

Kishony³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

157

191

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Cell size varies greatly among different types of cells, but the range in size that a specific cell type can reach is limited. A longstanding question in biology is how cells control their size. Escherichia coli adjusts size and growth rate according to the availability of nutrients so that it grows larger and faster in nutrient-rich media than in nutrient-poor media. Here, we describe how, using classical genetics, we have isolated a remarkably small E. coli mutant that has undergone a 70% reduction in cell volume with respect to wild type. This mutant lacks FabH, an enzyme involved in fatty acid biosynthesis that previously was thought to be essential for the viability of E. coli. We demonstrate that although FabH is not essential in wild-type E. coli, it is essential in cells that are defective in the production of the small-molecule and global regulator ppGpp. Furthermore, we have found that the loss of FabH causes a reduction in the rate of envelope growth and renders cells unable to regulate cell size properly in response to nutrient excess. Therefore we propose a model in which fatty acid biosynthesis plays a central role in regulating the size of E. coli cells in response to nutrient availability.acteria regulate their size and growth rate in response to nutrient availability. For example, Escherichia coli, Salmonella typhimurium, and Bacillus subtilis cells grow larger and faster in nutrient-rich medium than in nutrient-poor medium (1-6). Changes in temperature can alter growth rate but not size (2). Therefore, the size a cell attains depends on the nutritional composition of the growth medium, suggesting that nutrients affect a rate-limiting step(s) that controls size and the rate of growth.Bacteria must coordinate cell size, growth rate, and division in response to nutrient availability. Indeed, when E. coli changes its size, it also changes its generation time inversely; however, it maintains the cell mass-to-DNA ratio constant because it initiates DNA replication whenever it reaches a particular cell mass or a multiple of that mass (6). Interestingly, recent studies have shown that B. subtilis and E. coli use different regulatory mechanisms to couple cell size and DNA replication (4, 7). In E. coli DNA replication is not initiated until the cell reaches an appropriate size, but size does not affect the timing of replication in B. subtilis. Nevertheless, the amount of active DnaA, which unwinds DNA at the origin and thereby triggers replication (8, 9), is relevant in controlling the initiation of replication in both bacteria (7). Furthermore, a metabolic pathway for glucolipid biosynthesis regulates cell size in B. subtilis in response to nutrients under conditions that promote rapid growth (4). In this pathway, the UDP-glucose transferase UgtP inhibits the assembly of the divisome, the division machinery. The levels and localization of UgtP vary with nutrient availability so that assembly of the divisome is delayed under nutrient-rich conditions, resulting in longer cells.We do not understand how nu...

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Section: Loss Of Fabh Function Compromises Regulation Of Cell Size Inmentioning

confidence: 99%

“…For example, Escherichia coli, Salmonella typhimurium, and Bacillus subtilis cells grow larger and faster in nutrient-rich medium than in nutrient-poor medium (1)(2)(3)(4)(5)(6). Changes in temperature can alter growth rate but not size (2).…”

mentioning

confidence: 99%

Regulation of cell size in response to nutrient availability by fatty acid biosynthesis in Escherichia coli

Yao

Davis

Kishony³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

157

191

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“…The observed dissociation between the rates of RNA, DNA and protein syntheses and of nucleoid and cell division during a transition from one steady state to another were crucial in establishing the relationship between chromosome replication and cell division (9-11) and for pursuing studies on the mechanism of ribosomal biogenesis and the activity of the protein-synthesizing system (for reviews, see references 14 and 19). This approach also pointed to a way for discovering the mechanism of cell shape determination by the intriguing observation of length overshoot before the shifted cells attain their new steady-state dimensions (7,29).In spite of the prevalent statement that the new, higher rate of culture mass growth is achieved immediately after the shift to richer media (for example, see reference 22), a better approximation clearly describes it as a relatively slow process (31). This is due to the large changes in the repressioninduction patterns between two sets of genes required under It was therefore comforting to find shift-down conditions with virtually no modifications in the pattern of promoter activities, by suddenly reducing the carbon and energy source availability without replacing it.…”

mentioning

confidence: 99%

“…The resultant increase of cell size with growth rate, 1/, at least in Escherichia coli and Salmonella typhimurium, is associated with enlargement in both cell dimensions (length and diameter) (26,29,31) with very little change in shape (length/diameter ratio) (30). Mutants with an altered Mi have been isolated, and some biochemical steps have been deciphered (1,2,23,28), but the mechanisms that govern and integrate these processes (initiation and termination of chromosome replication, cell division and shape determination, and chromosome segregation) in the living cell are still obscure (for example, see reference 4).…”

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confidence: 99%

Rate maintenance of cell division in Escherichia coli B/r: analysis of a simple nutritional shift-down

Zaritsky

Helmstetter

1992

J Bacteriol

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A competitive (nonmetabolizable) inhibitor of glucose uptake, a-methylglucoside, was used to limit the growth ofEscherichia coli. Cell division during such a nutritional shift-down was studied in batch cultures and with the "baby-machine" technique. Following a brief delay, the rate of division was maintained for 60 to 70 min in batch cultures and for an extended period in the baby machine. Decreases in cell size were due, in part, to a possible reduction in the mass per chromosome origin at the time of replication initiation and a shorter time interval between initiation and the subsequent division. These unusual findings suggest that this method for abrupt change in growth rate without modifying repression patterns is useful for studying the control of various aspects of the bacterial cell.A bacterial cell divides C + D min after initiation of chromosome replication (10). Initiation capacity builds up during its preceding doubling time, T min. Cell mass at initiation is, to a first approximation, 27-multiple of a minimal value, Mi, where n is an integer greater than or equal to (C + D)/T (5, 25). The resultant increase of cell size with growth rate, 1/, at least in Escherichia coli and Salmonella typhimurium, is associated with enlargement in both cell dimensions (length and diameter) (26,29,31) with very little change in shape (length/diameter ratio) (30). Mutants with an altered Mi have been isolated, and some biochemical steps have been deciphered (1, 2, 23, 28), but the mechanisms that govern and integrate these processes (initiation and termination of chromosome replication, cell division and shape determination, and chromosome segregation) in the living cell are still obscure (for example, see reference 4).Much of our understanding of the physiology of a bacterial cell stems from the experimental procedure which perturbs the steady state of exponentially growing cultures in a well-controlled way, the nutritional shift-up (for example, see references 1 and 17-20; for a review, see reference 3). The observed dissociation between the rates of RNA, DNA and protein syntheses and of nucleoid and cell division during a transition from one steady state to another were crucial in establishing the relationship between chromosome replication and cell division (9-11) and for pursuing studies on the mechanism of ribosomal biogenesis and the activity of the protein-synthesizing system (for reviews, see references 14 and 19). This approach also pointed to a way for discovering the mechanism of cell shape determination by the intriguing observation of length overshoot before the shifted cells attain their new steady-state dimensions (7,29).In spite of the prevalent statement that the new, higher rate of culture mass growth is achieved immediately after the shift to richer media (for example, see reference 22), a better approximation clearly describes it as a relatively slow process (31). This is due to the large changes in the repressioninduction patterns between two sets of genes required under It was therefore comfort...

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“…Agar filtration is a common method of preparing Escherichia coli cells for electron microscopy in order to obtain size distributions of various kinds (3,10,17). This technique was first proposed by Kellenberger and Arber (6) and later improved by Woldringh et al (16).…”

mentioning

confidence: 99%

Shape changes in Escherichia coli B/r A during agar filtration

Vardi

Grover

1993

Cytometry

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We have investigated the phenomenon of shape distortion in a sample of 1,552 Escherichia coli Blr A cells in balanced exponential growth, during preparation for electron microscopy by agar filtration. Mixed preparations of bacterial cells and polystyrene latex spheres were shadow cast at low angle and the resulting shadows used to obtain quantitative estimates for the dimensions of the dehydrated cell; these then serve as a basis for a model of its shape in three dimensions. Key terms: Cell distortion, dehydration, dimensional changes, dryingAgar filtration is a common method of preparing Escherichia coli cells for electron microscopy in order to obtain size distributions of various kinds (3,10,17). This technique was first proposed by Kellenberger and Arber (6) and later improved by Woldringh et al. (16). Agar (2%) is made up in distilled water and dried to about 80% of its original weight. A perforated plastic membrane is superimposed by pouring a solution of 0.4% Parlodion (Mallinckrodt, St. Louis, MO) in amylacetate on the agar slant precooled below the dewpoint in order to induce the formation of tiny holes by water vapor condensation (2). Small drops of a suspension of cells fixed in 0.1-0.2% Os04 are deposited on the membrane and allowed to drain away; those that fail to do so within 60 min are rejected. The dimensions of a cell are determined by measuring the length and width of its projection in a transmission electron microscope (TEM).The deformation that must perforce be caused by the dehydration process (9,16) has cast doubt on the justification in representing the dimensions of a hydrated cell by the corresponding projections of its dehydrated counterpart (12), but such skepticism is far from universal (13,161. Moreover, the controversy cannot be settled simply by comparing TEM measurements with those obtained on living cells using light microscopy, even under phase contrast or Nomarski optics, because bacteria are very small (1.5 pm long by 0.5 pm in diameter, nominal dimensions) and any differences are expected to be well below effective optical resolution.In this article we attempt to estimate the effect of drying on bacterial cells, utilizing information inherent in the preparation itself. Low-angle shadow casting is used a t several morphologically defined locations to determine average values of cell height above the cellulose membrane. A model describing the structure of the dehydrated cell is then proposed, based on these results. Thus the difference between the mean width of aggregated and free cells is used to estimate the change in width that occurs during dehydration, whereas a n analysis of the fissures formed between cells aggregated during settling on the copper grid provides a n estimate for the change in length. The copper grids were photographed in focus on 70 mm film (SD-281, Kodak, Rochester, NY) using a TEM (EM300, Philips, Eindhoven, Netherlands) a t 60kV with a final magnification of ~3 , 6 0 0 ; exposure time was 1% s. MATERIALS AND METHODS

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Dimensional rearrangement of rod-shaped bacteria following nutritional shift-up. II. Experiments with Escherichia coli

Cited by 61 publications

References 25 publications

Regulation of cell size in response to nutrient availability by fatty acid biosynthesis in Escherichia coli

Regulation of cell size in response to nutrient availability by fatty acid biosynthesis in Escherichia coli

Rate maintenance of cell division in Escherichia coli B/r: analysis of a simple nutritional shift-down

Shape changes in Escherichia coli B/r A during agar filtration

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