scholarly journals Tad Pili Play a Dynamic Role in Caulobacter crescentus Surface Colonization

mBio ◽  
2019 ◽  
Vol 10 (3) ◽  
Author(s):  
Matteo Sangermani ◽  
Isabelle Hug ◽  
Nora Sauter ◽  
Thomas Pfohl ◽  
Urs Jenal
Keyword(s):  
Caulobacter Crescentus ◽  
Optical Trap ◽  
Model Organism ◽  
Natural Environments ◽  
Surface Attachment ◽  
Content Type ◽  
Surface Colonization ◽  
Bacterial Surface ◽  
Solid Media ◽  
Resilient Communities

ABSTRACT Bacterial surface attachment is mediated by filamentous appendages called pili. Here, we describe the role of Tad pili during surface colonization of Caulobacter crescentus. Using an optical trap and microfluidic controlled flow conditions to mimic natural environments, we demonstrated that Tad pili undergo repeated dynamic cycles of extension and retraction. Within seconds after establishing surface contact, pilus retraction reorients cells into an upright position, promoting walking-like movements against the medium flow. Pilus-mediated positioning of the flagellate pole close to the surface facilitates motor-mediated mechanical sensing and promotes anchoring of the holdfast, an adhesive substance that affords long-term attachment. We present evidence that the second messenger c-di-GMP regulates pilus dynamics during surface encounter in distinct ways, promoting increased activity at intermediate levels and retraction of pili at peak concentrations. We propose a model in which flagellum and Tad pili functionally interact and together impose a ratchet-like mechanism that progressively drives C. crescentus cells toward permanent surface attachment. IMPORTANCE Bacteria are able to colonize surfaces in environmental, industrial, and medical settings, where they form resilient communities called biofilms. In order to control bacterial surface colonization, microbiologists need to gain a detailed understanding of the processes that bacteria use to live at the liquid-surface interface and that allow them to adhere to and move on surfaces and eventually grow and persist on solid media. To facilitate these processes, bacteria are equipped with adhesive structures such as flagella and pili and with matrix components such as exopolysaccharides. How these cellular organelles are coordinated to optimize surface processes is currently subject to intense investigations. Here we used the model organism Caulobacter crescentus to demonstrate that polar pili are highly dynamic structures that are functionally interconnected with the flagellar motor to mediate surface sensing, thereby enforcing rapid and permanent surface attachment. These studies provide an entry point for an in-depth molecular analysis of bacterial surface colonization.

scholarly journals Tad pili play a dynamic role in Caulobacter crescentus surface colonization

2019 ◽  
Author(s):  
Matteo Sangermani ◽  
Isabelle Hug ◽  
Nora Sauter ◽  
Thomas Pfohl ◽  
Urs Jenal
Keyword(s):  
Caulobacter Crescentus ◽  
Optical Trap ◽  
Natural Environments ◽  
Surface Attachment ◽  
Surface Colonization ◽  
Bacterial Surface ◽  
Controlled Flow ◽  
Mechanical Sensing

ABSTRACTBacterial surface attachment is mediated by rotary flagella and filamentous appendages called pili. Here, we describe the role of Tad pili during surface colonization of Caulobacter crescentus. Using an optical trap and microfluidic controlled flow conditions as a mimic of natural environments, we demonstrate that Tad pili undergo repeated cycles of extension and retraction. Within seconds after establishing surface contact, pili reorient cells into an upright position promoting walking-like movements against the medium flow. Pili-mediated positioning of the flagellated pole close to the surface facilitates motor-mediated mechanical sensing and promotes anchoring of the holdfast, an adhesive substance that affords long-term attachment. We present evidence that the second messenger c-di-GMP regulates pili dynamics during surface encounter in distinct ways, promoting increased activity at intermediate levels and retraction of pili at peak concentrations. We propose a model, in which flagellum and Tad pili functionally interact and together impose a ratchet-like mechanism that progressively drives C. crescentus cells towards permanent surface attachment.

scholarly journals Flagellar Perturbations Activate Adhesion through Two Distinct Pathways in Caulobacter crescentus

mBio ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
David M. Hershey ◽  
Aretha Fiebig ◽  
Sean Crosson
Keyword(s):  
Caulobacter Crescentus ◽  
Mechanical Stimuli ◽  
Flagellar Motility ◽  
Surface Attachment ◽  
Content Type ◽  
Surface Colonization ◽  
Epistasis Analysis ◽  
Flagellar Assembly ◽  
Ecological Importance ◽  
Late Stages

ABSTRACT Bacteria carry out sophisticated developmental programs to colonize exogenous surfaces. The rotary flagellum, a dynamic machine that drives motility, is a key regulator of surface colonization. The specific signals recognized by flagella and the pathways by which those signals are transduced to coordinate adhesion remain subjects of debate. Mutations that disrupt flagellar assembly in the dimorphic bacterium Caulobacter crescentus stimulate the production of a polysaccharide adhesin called the holdfast. Using a genomewide phenotyping approach, we compared surface adhesion profiles in wild-type and flagellar mutant backgrounds of C. crescentus. We identified a diverse set of flagellar mutations that enhance adhesion by inducing a hyperholdfast phenotype and discovered a second set of mutations that suppress this phenotype. Epistasis analysis of the flagellar signaling suppressor (fss) mutations demonstrated that the flagellum stimulates holdfast production via two genetically distinct pathways. The developmental regulator PleD contributes to holdfast induction in mutants disrupted at both early and late stages of flagellar assembly. Mutants disrupted at late stages of flagellar assembly, which assemble an intact rotor complex, induce holdfast production through an additional process that requires the MotAB stator and its associated diguanylate cyclase, DgcB. We have assigned a subset of the fss genes to either the stator- or pleD-dependent networks and characterized two previously unidentified motility genes that regulate holdfast production via the stator complex. We propose a model through which the flagellum integrates mechanical stimuli into the C. crescentus developmental program to coordinate adhesion. IMPORTANCE Understanding how bacteria colonize solid surfaces is of significant clinical, industrial and ecological importance. In this study, we identified genes that are required for Caulobacter crescentus to activate surface attachment in response to signals from a macromolecular machine called the flagellum. Genes involved in transmitting information from the flagellum can be grouped into separate pathways, those that control the C. crescentus morphogenic program and those that are required for flagellar motility. Our results support a model in which a developmental and a mechanical signaling pathway operate in parallel downstream of the flagellum and converge to regulate adhesion. We conclude that the flagellum serves as a signaling hub by integrating internal and external cues to coordinate surface colonization and emphasize the role of signal integration in linking complex sets of environmental stimuli to individual behaviors.

scholarly journals Flagellar perturbations activate adhesion through two distinct pathways in Caulobacter crescentus

2020 ◽  
Author(s):  
David M. Hershey ◽  
Aretha Fiebig ◽  
Sean Crosson
Keyword(s):  
Caulobacter Crescentus ◽  
Mechanical Stimuli ◽  
Flagellar Motility ◽  
Surface Attachment ◽  
Surface Colonization ◽  
Epistasis Analysis ◽  
A Genome ◽  
Flagellar Assembly ◽  
Ecological Importance ◽  
Late Stages

AbstractBacteria carry out sophisticated developmental programs to colonize exogenous surfaces. The rotary flagellum, a dynamic machine that drives motility, is a key regulator of surface colonization. The specific signals recognized by flagella and the pathways by which those signals are transduced to coordinate adhesion remain subjects of debate. Mutations that disrupt flagellar assembly in the dimorphic bacterium Caulobacter crescentus stimulate the production of a polysaccharide adhesin called the holdfast. Using a genome-wide phenotyping approach, we compared surface adhesion profiles in wild-type and flagellar mutant backgrounds of C. crescentus. We identified a diverse set of flagellar mutations that enhance adhesion by inducing a hyper-holdfast phenotype and discovered a second set of mutations that suppress this phenotype. Epistasis analysis of the flagellar signaling suppressor (fss) mutations demonstrated that the flagellum stimulates holdfast production via two genetically distinct pathways. The developmental regulator PleD contributes to holdfast induction in mutants disrupted at both early and late stages of flagellar assembly. Mutants disrupted at late stages of flagellar assembly, which assemble an intact rotor complex, induce holdfast production through an additional process that requires the MotAB stator and its associated diguanylate cyclase, DgcB. We have assigned a subset of the fss genes to either the stator- or pleD-dependent networks and characterized two previously unidentified motility genes that regulate holdfast production via the stator complex. We propose a model through which the flagellum integrates mechanical stimuli into the C. crescentus developmental program to coordinate adhesion.ImportanceUnderstanding how bacteria colonize solid surfaces is of significant clinical, industrial and ecological importance. In this study, we identified genes that are required for Caulobacter crescentus to activate surface attachment in response to signals from a macromolecular machine called the flagellum. Genes involved in transmitting information from the flagellum can be grouped into separate pathways, those that control the C. crescentus morphogenic program and those that are required for flagellar motility. Our results support a model in which a developmental and a mechanical signaling pathway operate in parallel downstream of the flagellum and converge to regulate adhesion. We conclude that the flagellum serves as a signaling hub by integrating internal and external cues to coordinate surface colonization and emphasize the role of signal integration in linking complex sets of environmental stimuli to individual behaviors.

scholarly journals Regulation of Bacterial Cell Cycle Progression by Redundant Phosphatases

2020 ◽  
Vol 202 (17) ◽  
Author(s):  
Jérôme Coppine ◽  
Andreas Kaczmarczyk ◽  
Kenny Petit ◽  
Thomas Brochier ◽  
Urs Jenal ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Environmental Changes ◽  
Caulobacter Crescentus ◽  
Response Regulator ◽  
Model Organism ◽  
Replication Initiation ◽  
Cycle Progression ◽  
Content Type ◽  
Two Component

ABSTRACT In the model organism Caulobacter crescentus, a network of two-component systems involving the response regulators CtrA, DivK, and PleD coordinates cell cycle progression with differentiation. Active phosphorylated CtrA prevents chromosome replication in G1 cells while simultaneously regulating expression of genes required for morphogenesis and development. At the G1-S transition, phosphorylated DivK (DivK∼P) and PleD (PleD∼P) accumulate to indirectly inactivate CtrA, which triggers DNA replication initiation and concomitant cellular differentiation. The phosphatase PleC plays a pivotal role in this developmental program by keeping DivK and PleD phosphorylation levels low during G1, thereby preventing premature CtrA inactivation. Here, we describe CckN as a second phosphatase akin to PleC that dephosphorylates DivK∼P and PleD∼P in G1 cells. However, in contrast to PleC, no kinase activity was detected with CckN. The effects of CckN inactivation are largely masked by PleC but become evident when PleC and DivJ, the major kinase for DivK and PleD, are absent. Accordingly, mild overexpression of cckN restores most phenotypic defects of a pleC null mutant. We also show that CckN and PleC are proteolytically degraded in a ClpXP-dependent way before the onset of the S phase. Surprisingly, known ClpX adaptors are dispensable for PleC and CckN proteolysis, raising the possibility that as yet unidentified proteolytic adaptors are required for the degradation of both phosphatases. Since cckN expression is induced in stationary phase, depending on the stress alarmone (p)ppGpp, we propose that CckN acts as an auxiliary factor responding to environmental stimuli to modulate CtrA activity under suboptimal conditions. IMPORTANCE Two-component signal transduction systems are widely used by bacteria to adequately respond to environmental changes by adjusting cellular parameters, including the cell cycle. In Caulobacter crescentus, PleC acts as a phosphatase that indirectly protects the response regulator CtrA from premature inactivation during the G1 phase of the cell cycle. Here, we provide genetic and biochemical evidence that PleC is seconded by another phosphatase, CckN. The activity of PleC and CckN phosphatases is restricted to the G1 phase since both proteins are degraded by ClpXP protease before the G1-S transition. Degradation is independent of any known proteolytic adaptors and relies, in the case of CckN, on an unsuspected N-terminal degron. Our work illustrates a typical example of redundant functions between two-component proteins.

scholarly journals Social Cooperativity of Bacteria during Reversible Surface Attachment in Young Biofilms: a Quantitative Comparison of Pseudomonas aeruginosa PA14 and PAO1

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Calvin K. Lee ◽  
Jérémy Vachier ◽  
Jaime de Anda ◽  
Kun Zhao ◽  
Amy E. Baker ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Stochastic Model ◽  
Bacterial Biofilm ◽  
Population Increase ◽  
Pivotal Phase ◽  
Surface Attachment ◽  
Content Type ◽  
Cellular Behavior ◽  
Bacterial Surface ◽  
Surface Sensing

ABSTRACT What are bacteria doing during “reversible attachment,” the period of transient surface attachment when they initially engage a surface, besides attaching themselves to the surface? Can an attaching cell help any other cell attach? If so, does it help all cells or employ a more selective strategy to help either nearby cells (spatial neighbors) or its progeny (temporal neighbors)? Using community tracking methods at the single-cell resolution, we suggest answers to these questions based on how reversible attachment progresses during surface sensing for Pseudomonas aeruginosa strains PAO1 and PA14. Although PAO1 and PA14 exhibit similar trends of surface cell population increase, they show unanticipated differences when cells are considered at the lineage level and interpreted using the quantitative framework of an exactly solvable stochastic model. Reversible attachment comprises two regimes of behavior, processive and nonprocessive, corresponding to whether cells of the lineage stay on the surface long enough to divide, or not, before detaching. Stark differences between PAO1 and PA14 in the processive regime of reversible attachment suggest the existence of two surface colonization strategies. PAO1 lineages commit quickly to a surface compared to PA14 lineages, with early c-di-GMP-mediated exopolysaccharide (EPS) production that can facilitate the attachment of neighbors. PA14 lineages modulate their motility via cyclic AMP (cAMP) and retain memory of the surface so that their progeny are primed for improved subsequent surface attachment. Based on the findings of previous studies, we propose that the differences between PAO1 and PA14 are potentially rooted in downstream differences between Wsp-based and Pil-Chp-based surface-sensing systems, respectively. IMPORTANCE The initial pivotal phase of bacterial biofilm formation known as reversible attachment, where cells undergo a period of transient surface attachment, is at once universal and poorly understood. What is more, although we know that reversible attachment culminates ultimately in irreversible attachment, it is not clear how reversible attachment progresses phenotypically, as bacterial surface-sensing circuits fundamentally alter cellular behavior. We analyze diverse observed bacterial behavior one family at a time (defined as a full lineage of cells related to one another by division) using a unifying stochastic model and show that our findings lead to insights on the time evolution of reversible attachment and the social cooperative dimension of surface attachment in PAO1 and PA14 strains.

scholarly journals A Single-Domain Response Regulator Functions as an Integrating Hub To Coordinate General Stress Response and Development in Alphaproteobacteria

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
C. Lori ◽  
A. Kaczmarczyk ◽  
I. de Jong ◽  
U. Jenal
Keyword(s):  
Stress Response ◽  
Histidine Kinase ◽  
Caulobacter Crescentus ◽  
Response Regulator ◽  
Model Organism ◽  
Single Domain ◽  
Content Type ◽  
General Stress Response ◽  
General Stress ◽  
Phosphoryl Groups

ABSTRACTThe alphaproteobacterial general stress response is governed by a conserved partner-switching mechanism that is triggered by phosphorylation of the response regulator PhyR. In the model organismCaulobacter crescentus, PhyR was proposed to be phosphorylated by the histidine kinase PhyK, but biochemical evidence in support of such a role of PhyK is missing. Here, we identify a single-domain response regulator, MrrA, that is essential for general stress response activation inC. crescentus. We demonstrate that PhyK does not function as a kinase but accepts phosphoryl groups from MrrA and passes them on to PhyR, adopting the role of a histidine phosphotransferase. MrrA is phosphorylated by at least six histidine kinases that likely serve as stress sensors. MrrA also transfers phosphate to LovK, a histidine kinase involved inC. crescentusholdfast production and attachment, which also negatively regulates the general stress response. We show that LovK together with the response regulator LovR acts as a phosphate sink to redirect phosphate flux away from the PhyKR branch. In agreement with the biochemical data, anmrrAmutant is unable to activate the general stress response and shows a hyperattachment phenotype, which is linked to decreased expression of the major holdfast inhibitory protein HfiA. We propose that MrrA serves as a central phosphorylation hub that coordinates the general stress response withC. crescentusdevelopment and other adaptive behaviors. The characteristic bow-tie architecture of this phosphorylation network with MrrA as the central knot may expedite the evolvability and species-specific niche adaptation of this group of bacteria.IMPORTANCETwo-component systems (TCSs) consisting of a histidine kinase and a cognate response regulator are predominant signal transduction systems in bacteria. To avoid cross talk, TCSs are generally thought to be highly insulated from each other. However, this notion is based largely on studies of the HisKA subfamily of histidine kinases, while little information is available for the HWE and HisKA2 subfamilies. The latter have been implicated in the alphaproteobacterial general stress response. Here, we show that in the model organismCaulobacter crescentusan atypical FATGUY-type single-domain response regulator, MrrA, is highly promiscuous in accepting and transferring phosphoryl groups from and to multiple up- and downstream kinases, challenging the current view of strictly insulated TCSs. Instead, we propose that FATGUY response regulators have evolved in alphaproteobacteria as central phosphorylation hubs to broadly sample information and distribute phosphoryl groups between the general stress response pathway and other TCSs, thereby coordinating multiple cellular behaviors.

scholarly journals Obstruction of pilus retraction stimulates bacterial surface sensing

2017 ◽  
Author(s):  
Courtney K. Ellison ◽  
Jingbo Kan ◽  
Rebecca S. Dillard ◽  
David T. Kysela ◽  
Cheri M. Hampton ◽  
...  
Keyword(s):  
Genetic Modification ◽  
Caulobacter Crescentus ◽  
Physiological Changes ◽  
Type Iv Pilus ◽  
Dynamic Nature ◽  
Surface Attachment ◽  
Bacterial Surface ◽  
Type Iv ◽  
Surface Sensing ◽  
Surface Contact

AbstractSurface association provides numerous fitness advantages to bacteria. Thus, it is critical for bacteria to recognize surface contact and to consequently initiate physiological changes required for a surface-associated lifestyle (1). Ubiquitous microbial appendages called pili are involved in sensing surfaces and mediating downstream surface-associated behaviors (2–6). The mechanism by which pili mediate surface sensing remains unknown, largely due to the difficulty to visualize their dynamic nature and to directly modulate their activity without genetic modification. Here, we show thatCaulobacter crescentuspili undergo dynamic cycles of extension and retraction that cease within seconds of surface contact, and this arrest of pilus activity coincides with surface-stimulated holdfast synthesis. By physically blocking pili, we show that imposing resistance to pilus retraction is sufficient to stimulate holdfast synthesis in the absence of surface contact. Thus, resistance to type IV pilus retraction upon surface attachment is used for surface sensing.One Sentence SummaryBacteria use the tension imparted on retracting pilus fibers upon their binding to a surface for surface sensing.

scholarly journals Cyclic di-GMP differentially tunes a bacterial flagellar motor through a novel class of CheY-like regulators

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Jutta Nesper ◽  
Isabelle Hug ◽  
Setsu Kato ◽  
Chee-Seng Hee ◽  
Judith Maria Habazettl ◽  
...  
Keyword(s):  
Motor Activity ◽  
Caulobacter Crescentus ◽  
Chemical Information ◽  
Flagellar Motor ◽  
Cellular Functions ◽  
Surface Attachment ◽  
Chemical Proteomics ◽  
Bacterial Surface ◽  
Rotary Machine ◽  
Motile Cells

The flagellar motor is a sophisticated rotary machine facilitating locomotion and signal transduction. Owing to its important role in bacterial behavior, its assembly and activity are tightly regulated. For example, chemotaxis relies on a sensory pathway coupling chemical information to rotational bias of the motor through phosphorylation of the motor switch protein CheY. Using a chemical proteomics approach, we identified a novel family of CheY-like (Cle) proteins in Caulobacter crescentus, which tune flagellar activity in response to binding of the second messenger c-di-GMP to a C-terminal extension. In their c-di-GMP bound conformation Cle proteins interact with the flagellar switch to control motor activity. We show that individual Cle proteins have adopted discrete cellular functions by interfering with chemotaxis and by promoting rapid surface attachment of motile cells. This study broadens the regulatory versatility of bacterial motors and unfolds mechanisms that tie motor activity to mechanical cues and bacterial surface adaptation.

scholarly journals Comparative Analysis of Ionic Strength Tolerance between Freshwater and MarineCaulobacteralesAdhesins

2019 ◽  
Vol 201 (18) ◽  
Author(s):  
Nelson K. Chepkwony ◽  
Cécile Berne ◽  
Yves V. Brun
Keyword(s):  
Ionic Strength ◽  
Physicochemical Properties ◽  
Bacterial Adhesion ◽  
Marine Bacterium ◽  
Caulobacter Crescentus ◽  
High Ionic Strength ◽  
Chemical Compositions ◽  
Shear Forces ◽  
Surface Attachment ◽  
Content Type

ABSTRACTBacterial adhesion is affected by environmental factors, such as ionic strength, pH, temperature, and shear forces. Therefore, marine bacteria must have developed adhesins with different compositions and structures than those of their freshwater counterparts to adapt to their natural environment. The dimorphic alphaproteobacteriumHirschia balticais a marine budding bacterium in the cladeCaulobacterales.H. balticauses a polar adhesin, the holdfast, located at the cell pole opposite the reproductive stalk, for surface attachment and cell-cell adhesion. The holdfast adhesin has been best characterized inCaulobacter crescentus, a freshwater member of theCaulobacterales, and little is known about holdfast compositions and properties in marineCaulobacterales. Here, we useH. balticaas a model to characterize holdfast properties in marineCaulobacterales. We show that freshwater and marineCaulobacteralesuse similar genes in holdfast biogenesis and that these genes are highly conserved among the species in the two genera. We determine thatH. balticaproduces a larger holdfast thanC. crescentusand that the holdfasts have different chemical compositions, as they containN-acetylglucosamine and galactose monosaccharide residues and proteins but lack DNA. Finally, we show thatH. balticaholdfasts tolerate higher ionic strength than those ofC. crescentus. We conclude that marineCaulobacteralesholdfasts have physicochemical properties that maximize binding in high-ionic-strength environments.IMPORTANCEMost bacteria spend a large part of their life spans attached to surfaces, forming complex multicellular communities called biofilms. Bacteria can colonize virtually any surface, and therefore, they have adapted to bind efficiently in very different environments. In this study, we compare the adhesive holdfasts produced by the freshwater bacteriumC. crescentusand a relative, the marine bacteriumH. baltica. We show thatH. balticaholdfasts have a different morphology and chemical composition and tolerate high ionic strength. Our results show that theH. balticaholdfast is an excellent model to study the effect of ionic strength on adhesion and provides insights into the physicochemical properties required for adhesion in the marine environment.

scholarly journals Proper Control of Caulobacter crescentus Cell Surface Adhesion Requires the General Protein Chaperone DnaK

2016 ◽  
Vol 198 (19) ◽  
pp. 2631-2642 ◽  
Author(s):  
Daniel S. Eaton ◽  
Sean Crosson ◽  
Aretha Fiebig
Keyword(s):  
Cell Adhesion ◽  
Caulobacter Crescentus ◽  
Surface Adhesion ◽  
Surface Attachment ◽  
Small Protein ◽  
Content Type ◽  
Chaperone Dnak ◽  
Protein Chaperone ◽  
General Protein ◽  
Lid Domain

ABSTRACTGrowth in a surface-attached bacterial community, or biofilm, confers a number of advantages. However, as a biofilm matures, high-density growth imposes stresses on individual cells, and it can become less advantageous for progeny to remain in the community. Thus, bacteria employ a variety of mechanisms to control attachment to and dispersal from surfaces in response to the state of the environment. The freshwater oligotrophCaulobacter crescentuscan elaborate a polysaccharide-rich polar organelle, known as the holdfast, which enables permanent surface attachment. Holdfast development is strongly inhibited by the small protein HfiA; mechanisms that control HfiA levels in the cell are not well understood. We have discovered a connection between the essential general protein chaperone, DnaK, and control ofC. crescentusholdfast development.C. crescentusmutants partially or completely lacking the C-terminal substrate binding “lid” domain of DnaK exhibit enhanced bulk surface attachment. Partial or complete truncation of the DnaK lid domain increases the probability that any single cell will develop a holdfast by 3- to 10-fold. These results are consistent with the observation that steady-state levels of an HfiA fusion protein are significantly diminished in strains that lack the entire lid domain of DnaK. While dispensable for growth, the lid domain ofC. crescentusDnaK is required for proper chaperone function, as evidenced by observed dysregulation of HfiA and holdfast development in strains expressing lidless DnaK mutants. We conclude that DnaK is an important molecular determinant of HfiA stability and surface adhesion control.IMPORTANCERegulatory control of cell adhesion ensures that bacterial cells can transition between free-living and surface-attached states. We define a role for the essential protein chaperone, DnaK, in the control ofCaulobacter crescentuscell adhesion.C. crescentussurface adhesion is mediated by an envelope-attached organelle known as the holdfast. Holdfast development is tightly controlled by HfiA, a small protein inhibitor that directly interacts with a WecG/TagA-family glycosyltransferase required for holdfast biosynthesis. We demonstrate that the C-terminal lid domain of DnaK is not essential for growth but is necessary for proper control of HfiA levels in the cell and for control of holdfast adhesin development.

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