The mechanisms that restrict peptidoglycan biosynthesis to the pole during elongation and re‐direct peptidoglycan biosynthesis to mid‐cell during cell division in polar‐growing Alphaproteobacteria are largely unknown. Here, we explore the role of early division proteins of
- Award ID(s):
- 1752024
- NSF-PAR ID:
- 10439359
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 120
- Issue:
- 11
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary Agrobacterium tumefaciens including three FtsZ homologs, FtsA and FtsW in the transition from polar growth to mid‐cell growth and ultimately cell division. Although two of the three FtsZ homologs localize to mid‐cell, exhibit GTPase activity and form co‐polymers, only one, FtsZAT, is required for cell division. We find that FtsZATis required not only for constriction and cell separation, but also for initiation of peptidoglycan synthesis at mid‐cell and cessation of polar peptidoglycan biosynthesis. Depletion of FtsZATinA. tumefaciens causes a striking phenotype: cells are extensively branched and accumulate growth active poles through tip splitting events. When cell division is blocked at a later stage by depletion of FtsA or FtsW, polar growth is terminated and ectopic growth poles emerge from mid‐cell. Overall, this work suggests thatA. tumefaciens FtsZ makes distinct contributions to the regulation of polar growth and cell division. -
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ABSTRACT Ribosomes—the primary macromolecular machines responsible for translating the genetic code into proteins—are complexes of precisely folded RNA and proteins. The ways in which their production and assembly are managed by the living cell is of deep biological importance. Here we extend a recent spatially resolved whole‐cell model of ribosome biogenesis in a fixed volume [Earnest et al., Biophys J 2015, 109, 1117–1135] to include the effects of growth, DNA replication, and cell division. All biological processes are described in terms of reaction‐diffusion master equations and solved stochastically using the Lattice Microbes simulation software. In order to determine the replication parameters, we construct and analyze a series of
Escherichia coli strains with fluorescently labeled genes distributed evenly throughout their chromosomes. By measuring these cells’ lengths and number of gene copies at the single‐cell level, we could fit a statistical model of the initiation and duration of chromosome replication. We found that for our slow‐growing (120 min doubling time)E. coli cells, replication was initiated 42 min into the cell cycle and completed after an additional 42 min. While simulations of the biogenesis model produce the correct ribosome and mRNA counts over the cell cycle, the kinetic parameters for transcription and degradation are lower than anticipated from a recent analytical time dependent model of in vivo mRNA production. Describing expression in terms of a simple chemical master equation, we show that the discrepancies are due to the lack of nonribosomal genes in the extended biogenesis model which effects the competition of mRNA for ribosome binding, and suggest corrections to parameters to be used in the whole‐cell model when modeling expression of the entire transcriptome. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 735–751, 2016. -
Glass, Jennifer B. (Ed.)ABSTRACT Standard methods for calculating microbial growth rates (μ) through the use of proxies, such as in situ fluorescence, cell cycle, or cell counts, are critical for determining the magnitude of the role bacteria play in marine carbon (C) and nitrogen (N) cycles. Taxon-specific growth rates in mixed assemblages would be useful for attributing biogeochemical processes to individual species and understanding niche differentiation among related clades, such as found in Synechococcus and Prochlorococcus . We tested three novel DNA sequencing-based methods (iRep, bPTR, and GRiD) for evaluating the growth of light-synchronized Synechococcus cultures under different light intensities and temperatures. In vivo fluorescence and cell cycle analysis were used to obtain standard estimates of growth rate for comparison with those of the sequence-based methods (SBM). None of the SBM values were correlated with growth rates calculated by standard techniques despite the fact that all three SBM were correlated with the percentage of cells in S phase (DNA replication) over the diel cycle. Inaccuracy in determining the time of maximum DNA replication is unlikely to account entirely for the absence of a relationship between SBM and growth rate, but the fact that most microbes in the surface ocean exhibit some degree of diel cyclicity is a caution for application of these methods. SBM correlate with DNA replication but cannot be interpreted quantitatively in terms of growth rate. IMPORTANCE Small but abundant, cyanobacterial strains such as the photosynthetic Synechococcus spp. are important because they contribute significantly to primary productivity in the ocean. These bacteria generate oxygen and provide biologically available carbon, which is essential for organisms at higher trophic levels. The small size and diversity of natural microbial assemblages mean that taxon-specific activities (e.g., growth rate) are difficult to obtain in the field. It has been suggested that sequence-based methods (SBM) may be able to solve this problem. We find, however, that SBM can detect DNA replication and are correlated with phases of the cell cycle but cannot be interpreted in terms of absolute growth rate for Synechococcus cultures growing under a day-night cycle, like that experienced in the ocean.more » « less
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Cellular differentiation is a fundamental strategy used by cells to generate specialized functions at specific stages of development. The bacterium
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2214796120
