Dataset Information

Flagellar Mutants Have Reduced Pilus Synthesis in Caulobacter crescentus.

ABSTRACT: Surface appendages, such as flagella and type IV pili, mediate a broad range of bacterial behaviors, including motility, attachment, and surface sensing. While many species harbor both flagella and type IV pili, little is known about how or if their syntheses are coupled. Here, we show that deletions of genes encoding different flagellum machinery components result in a reduction of pilus synthesis in Caulobacter crescentus First, we show that different flagellar mutants exhibit different levels of sensitivity to a pilus-dependent phage and that fewer cells within populations of flagellar mutants make pili. Furthermore, we find that single cells within flagellar mutant populations produce fewer pili per cell. We demonstrate that these gene deletions result in reduced transcription of pilus-associated genes and have a slight but significant effect on general transcription profiles. Finally, we show that the decrease in pilus production is due to a reduction in the pool of pilin subunits that are polymerized into pilus fibers. These data demonstrate that mutations in flagellar gene components not only affect motility but also can have considerable and unexpected consequences for other aspects of cell biology.IMPORTANCE Most bacterial species synthesize surface-exposed appendages that are important for environmental interactions and survival under diverse conditions. It is often assumed that these appendages act independently of each other and that mutations in either system can be used to assess functionality in specific processes. However, we show that mutations in flagellar genes can impact the production of type IV pili, as well as alter general RNA transcriptional profiles compared to a wild-type strain. These data demonstrate that seemingly simple mutations can broadly affect cell-regulatory networks.

SUBMITTER: Ellison CK

PROVIDER: S-EPMC6707913 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Flagellar Mutants Have Reduced Pilus Synthesis in <i>Caulobacter crescentus</i>.

Ellison Courtney K CK Rusch Douglas B DB Brun Yves V YV

Journal of bacteriology 20190822 18

Surface appendages, such as flagella and type IV pili, mediate a broad range of bacterial behaviors, including motility, attachment, and surface sensing. While many species harbor both flagella and type IV pili, little is known about how or if their syntheses are coupled. Here, we show that deletions of genes encoding different flagellum machinery components result in a reduction of pilus synthesis in <i>Caulobacter crescentus</i> First, we show that different flagellar mutants exhibit different ...[more]

PMID: 30833355

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Project description:Attachment is essential for microorganisms to establish interactions with both biotic and abiotic surfaces. Stable attachment of Caulobacter crescentus to surfaces requires an adhesive polysaccharide holdfast, but the exact composition of the holdfast is unknown. The holdfast is anchored to the cell envelope by outer membrane proteins HfaA, HfaB, and HfaD. Holdfast anchor gene mutations result in holdfast shedding and reduced cell adherence. Translocation of HfaA and HfaD to the cell surface requires HfaB. The Wzx homolog HfsF is predicted to be a bacterial polysaccharide flippase. An hfsF deletion significantly reduced the amount of holdfast produced per cell and slightly reduced adherence. A ?hfsF ?hfaD double mutant was completely deficient in adherence. A suppressor screen that restored adhesion in the ?hfsF ?hfaD mutant identified mutations in three genes: wbqV, rfbB, and rmlA Both WbqV and RfbB belong to a family of nucleoside-diphosphate epimerases, and RmlA has similarity to nucleotidyltransferases. The loss of wbqV or rfbB in the ?hfsF ?hfaD mutant reduced holdfast shedding but did not restore holdfast synthesis to parental levels. Loss of wbqV or rfbB did not restore adherence to a ?hfsF mutant but did restore adherence and holdfast anchoring to a ?hfaD mutant, confirming that suppression occurs through restoration of holdfast anchoring. The adherence and holdfast anchoring of a ?hfaA ?hfaD mutant could be restored by wbqV or rfbB mutation, but such mutations could not suppress these phenotypes in the ?hfaB mutant. We hypothesize that HfaB plays an additional role in holdfast anchoring or helps to translocate an unknown factor that is important for holdfast anchoring.IMPORTANCE Biofilm formation results in increased resistance to both environmental stresses and antibiotics. Caulobacter crescentus requires an adhesive holdfast for permanent attachment and biofilm formation, but the exact mechanism of polysaccharide anchoring to the cell and the holdfast composition are unknown. Here we identify novel polysaccharide genes that affect holdfast anchoring to the cell. We identify a new role for the holdfast anchor protein HfaB. This work increases our specific knowledge of the polysaccharide adhesin involved in Caulobacter attachment and the general knowledge regarding production and anchoring of polysaccharide adhesins by bacteria. This work also explores the interactions between different polysaccharide biosynthesis and secretion systems in bacteria.

Dataset Information

Flagellar Mutants Have Reduced Pilus Synthesis in Caulobacter crescentus.

Publications

Flagellar Mutants Have Reduced Pilus Synthesis in <i>Caulobacter crescentus</i>.

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