Defining the daughter swarmer cell

Bacteria encounter elevated copper (Cu) concentrations in multiple environments, varying from mining wastes to antimicrobial applications of copper. As the role of the environment in the bacterial response to Cu ion exposure remains elusive, we used a tagRNA-seq approach to elucidate the disparate responses of two morphotypes of Caulobacter crescentus NA1000 to moderate Cu stress in a complex rich (PYE) medium and a defined poor (M2G) medium. The transcriptome was more responsive in M2G, where we observed an extensive oxidative stress response and reconfiguration of the proteome, as well as the induction of metal resistance clusters. In PYE, little evidence was found for an oxidative stress response, but several transport systems were differentially expressed, and an increased need for histidine was apparent. These results show that the Cu stress response is strongly dependent on the cellular environment. In addition, induction of the extracytoplasmic function sigma factor SigF and its regulon was shared by the Cu stress responses in both media, and its central role was confirmed by the phenotypic screening of a sigF::Tn5 mutant. In both media, stalked cells were more responsive to Cu stress than swarmer cells, and a stronger basal expression of several cell protection systems was noted, indicating that the swarmer cell is inherently more Cu resistant. Our approach also allowed for detecting several new transcription start sites, putatively indicating small regulatory RNAs, and additional levels of Cu-responsive regulation.

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Timing of swarmer cell cycle morphogenesis and macromolecular synthesis by Hyphomicrobium neptunium in synchronous culture.

Journal of Bacteriology ◽

10.1128/jb.144.1.406-412.1980 ◽

1980 ◽

Vol 144 (1) ◽

pp. 406-412 ◽

Cited By ~ 19

Author(s):

T M Wali ◽

G R Hudson ◽

D A Danald ◽

R M Weiner

Keyword(s):

Cell Cycle ◽

Synchronous Culture ◽

Macromolecular Synthesis ◽

Swarmer Cell

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Swarmer cell development of the bacteriumProteus mirabilisrequires the conserved ECA biosynthesis gene,rffG

10.1101/198622 ◽

2017 ◽

Author(s):

Kristin Little ◽

Murray J. Tipping ◽

Karine A. Gibbs

Keyword(s):

Cell Morphology ◽

Stress Responses ◽

Cell Elongation ◽

Cell Envelope ◽

Membrane Composition ◽

Swarmer Cell ◽

Enterobacterial Common Antigen ◽

Envelope Stress ◽

Open Question ◽

Additional Role

AbstractIndividual cells of the bacteriumProteus mirabiliscan elongate up to 40-fold on surfaces before engaging in a cooperative surface-based motility termed swarming. How cells regulate this dramatic morphological remodeling remains an open question. In this paper, we move forward the understanding of this regulation by demonstrating thatP. mirabilisrequires the generffGfor swarmer cell elongation and subsequent swarm motility. TherffGgene encodes a protein homologous to the dTDP-glucose 4,6 dehydratase protein ofEscherichia coli, which contributes to Enterobacterial Common Antigen biosynthesis. Here we characterize therffGgene inP. mirabilis, demonstrating that it is required for the production of large lipopolysaccharide-linked moieties necessary for wild-type cell envelope integrity. We show that absence of therffGgene induces several stress-responsive pathways including those controlled by the transcriptional regulators RpoS, CaiF, and RcsB. We further show that inrffG-deficient cells, suppression of the Rcs phosphorelay, via loss of RcsB, is sufficient to induce cell elongation and swarm motility. However, loss of RcsB does not rescue cell envelope integrity defects and instead results in abnormally shaped cells, including cells producing more than two poles. We conclude that a RcsB-mediated response acts to suppress emergence of shape defects in cell envelope-compromised cells, suggesting an additional role for RcsB in maintaining cell morphology under stress conditions. We further propose that the composition of the cell envelope acts as a checkpoint before cells initiate swarmer cell elongation and motility.Importance statementP. mirabilisswarm motility has been implicated in pathogenesis. We have found that cells deploy multiple uncharacterized strategies to handle cell envelope stress beyond the Rcs phosphorelay when attempting to engage in swarm motility. While RcsB is known to directly inhibit the master transcriptional regulator for swarming, we have shown an additional role for RcsB in protecting cell morphology. These data support a growing appreciation that the Rcs phosphorelay is a multi-functional regulator of cell morphology in addition to its role in microbial stress responses. These data also strengthen the paradigm that outer membrane composition is a crucial checkpoint for modulating entry into swarm motility. Furthermore, therffG-dependent moieties provide a novel, attractive target for potential antimicrobials.

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Bacterial Swarming Reduces Proteus mirabilis and Vibrio parahaemolyticus Cell Stiffness and Increases β-Lactam Susceptibility

mBio ◽

10.1128/mbio.00210-19 ◽

2019 ◽

Vol 10 (5) ◽

Cited By ~ 2

Author(s):

George K. Auer ◽

Piercen M. Oliver ◽

Manohary Rajendram ◽

Ti-Yu Lin ◽

Qing Yao ◽

...

Keyword(s):

Cell Wall ◽

Osmotic Pressure ◽

Proteus Mirabilis ◽

Vibrio Parahaemolyticus ◽

Cell Stiffness ◽

Bending Rigidity ◽

Vegetative Cells ◽

Swarmer Cell ◽

Content Type ◽

Peptidoglycan Layer

ABSTRACT Swarmer cells of the Gram-negative uropathogenic bacteria Proteus mirabilis and Vibrio parahaemolyticus become long (>10 to 100 μm) and multinucleate during their growth and motility on polymer surfaces. We demonstrated that the increasing cell length is accompanied by a large increase in flexibility. Using a microfluidic assay to measure single-cell mechanics, we identified large differences in the swarmer cell stiffness (bending rigidity) of P. mirabilis (5.5 × 10−22 N m2) and V. parahaemolyticus (1.0 × 10−22 N m2) compared to vegetative cells (1.4 × 10−20 N m2 and 2.2 × 10−22 N m2, respectively). The reduction in bending rigidity (∼2-fold to ∼26-fold) was accompanied by a decrease in the average polysaccharide strand length of the peptidoglycan layer of the cell wall from 28 to 30 disaccharides to 19 to 22 disaccharides. Atomic force microscopy revealed a reduction in P. mirabilis peptidoglycan thickness from 1.5 nm (vegetative cells) to 1.0 nm (swarmer cells), and electron cryotomography indicated changes in swarmer cell wall morphology. P. mirabilis and V. parahaemolyticus swarmer cells became increasingly sensitive to osmotic pressure and susceptible to cell wall-modifying antibiotics (compared to vegetative cells)—they were ∼30% more likely to die after 3 h of treatment with MICs of the β-lactams cephalexin and penicillin G. The adaptive cost of “swarming” was offset by the increase in cell susceptibility to physical and chemical changes in their environment, thereby suggesting the development of new chemotherapies for bacteria that leverage swarming for the colonization of hosts and for survival. IMPORTANCE Proteus mirabilis and Vibrio parahaemolyticus are bacteria that infect humans. To adapt to environmental changes, these bacteria alter their cell morphology and move collectively to access new sources of nutrients in a process referred to as “swarming.” We found that changes in the composition and thickness of the peptidoglycan layer of the cell wall make swarmer cells of P. mirabilis and V. parahaemolyticus more flexible (i.e., reduce cell stiffness) and that they become more sensitive to osmotic pressure and cell wall-targeting antibiotics (e.g., β-lactams). These results highlight the importance of assessing the extracellular environment in determining antibiotic doses and the use of β-lactam antibiotics for treating infections caused by swarmer cells of P. mirabilis and V. parahaemolyticus.

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Proteus mirabilis mutants defective in swarmer cell differentiation and multicellular behavior.

Journal of Bacteriology ◽

10.1128/jb.173.19.6279-6288.1991 ◽

1991 ◽

Vol 173 (19) ◽

pp. 6279-6288 ◽

Cited By ~ 58

Author(s):

R Belas ◽

D Erskine ◽

D Flaherty

Keyword(s):

Cell Differentiation ◽

Proteus Mirabilis ◽

Swarmer Cell

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Global Regulation of Gene Expression and Cell Differentiation in Caulobacter crescentus in Response to Nutrient Availability

Journal of Bacteriology ◽

10.1128/jb.01240-09 ◽

2009 ◽

Vol 192 (3) ◽

pp. 819-833 ◽

Cited By ~ 28

Author(s):

Jennifer C. England ◽

Barrett S. Perchuk ◽

Michael T. Laub ◽

James W. Gober

Keyword(s):

Gene Expression ◽

Nitrogen Limitation ◽

Caulobacter Crescentus ◽

Regulation Of Gene Expression ◽

Fixed Time ◽

Natural Environments ◽

Swarmer Cell ◽

Regulatory Strategies ◽

Time Period ◽

Regulated Gene Expression

ABSTRACT In a developmental strategy designed to efficiently exploit and colonize sparse oligotrophic environments, Caulobacter crescentus cells divide asymmetrically, yielding a motile swarmer cell and a sessile stalked cell. After a relatively fixed time period under typical culture conditions, the swarmer cell differentiates into a replicative stalked cell. Since differentiation into the stalked cell type is irreversible, it is likely that environmental factors such as the availability of essential nutrients would influence the timing of the decision to abandon motility and adopt a sessile lifestyle. We measured two different parameters in nutrient-limited chemostat cultures, biomass concentration and the ratio of nonstalked to stalked cells, over a range of flow rates and found that nitrogen limitation significantly extended the swarmer cell life span. The transcriptional profiling experiments described here generate the first comprehensive picture of the global regulatory strategies used by an oligotroph when confronted with an environment where key macronutrients are sparse. The pattern of regulated gene expression in nitrogen- and carbon-limited cells shares some features in common with most copiotrophic organisms, but critical differences suggest that Caulobacter, and perhaps other oligotrophs, have evolved regulatory strategies to deal distinctly with their natural environments. We hypothesize that nitrogen limitation extends the swarmer cell lifetime by delaying the onset of a sequence of differentiation events, which when initiated by the correct combination of external environmental cues, sets the swarmer cell on a path to differentiate into a stalked cell within a fixed time period.

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