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 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 Bridging worlds: community led visual methods amidst climate change related disasters in Australia

2019 ◽  
Vol 29 (Supplement_4) ◽  
Author(s):  
C Macdougall ◽  
L Gibbs
Keyword(s):  
Climate Change ◽  
Rural Communities ◽  
Service Providers ◽  
Natural Environments ◽  
Visual Methods ◽  
Community Recovery ◽  
Visual Record ◽  
And Control

Abstract Background In February 2009 Victorian rural communities were hit by the worst bushfires in Australian history. Immediately we evaluated community groups preparing residents for bushfires. Ten years on, we are one of the few teams to evaluate medium to long term community recovery using multiple methods. As climate change becomes more visible, the frequency and intensity of disasters will increase so communities, governments and service providers need more evidence based strategies and policies. We explore how participant led visual methods provide new knowledge. Methods In study 1 participants in 3 of 7 focus groups in peoples’ homes spontaneously brought photos for us to examine before the discussions. In another participants spoke of the importance of photos they took at the time. We returned to the field to interview people in their homes about the meaning and role of photos. Results Participants wanted to inform us-as outsiders-of the awe and enormity of the fires. They created a visual record to communicate with key interest groups and ward off complacity as memories receded. Photos helped them construct timelines and meanings of the intense fires. Crucially, they recorded recovery and rebuilding in both the built and natural environments. Over the next ten years we chronicled stories from community led visual methods of communication, recovery and empowerment. We incorporated into qualitative methods participant led tours of their environments, with visual methods. Visual data collected by communities focused more strongly on the natural environment than researcher led verbal methods. Conclusions Visual sociology changes as technology provides participants in research with increased access to, and control over, visual methods. These changes can rebalance power relations between qualitative researchers and participants and bridge visual and verbal methods; crafting striking stories to influence those Australian policies unresponsive to climate change. Key messages Technological change enables participants in qualitative research to initiate visual methods to build bridges between them and researchers. Community led visual methods provide new types of data useful for theory and knowledge translation.

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 More than a feeling: microscopy approaches to understanding surface-sensing mechanisms

2020 ◽  
Author(s):  
Katherine J. Graham ◽  
Lori L. Burrows
Keyword(s):  
Live Cells ◽  
Surface Attachment ◽  
Bacterial Surface ◽  
Structural Modifications ◽  
Structure And Dynamics ◽  
Type Iv ◽  
Surface Sensing ◽  
Two Component Signal Transduction ◽  
Sense And Respond

The mechanisms by which bacteria sense and respond to surface attachment have long been a mystery. Our understanding of the structure and dynamics of bacterial appendages, notably type IV pili (T4P), provided new insights into the potential ways that bacteria sense surfaces. T4P are ubiquitous, retractable hair-like adhesins that until recently were difficult to image in the absence of fixation due to their nanoscale size. This review focuses on recent microscopy innovations used to visualize T4P in live cells to reveal the dynamics of their retraction and extension. We discuss recently proposed mechanisms by which T4P facilitate bacterial surface sensing, including the role of surface-exposed PilY1, two-component signal transduction pathways, force-induced structural modifications of the major pilin, and altered dynamics of the T4P motor complex.

scholarly journals Vibrio choleraefilamentation promotes chitin surface attachment at the expense of competition in biofilms

2019 ◽  
Vol 116 (28) ◽  
pp. 14216-14221 ◽  
Author(s):  
Benjamin R. Wucher ◽  
Thomas M. Bartlett ◽  
Mona Hoyos ◽  
Kai Papenfort ◽  
Alexandre Persat ◽  
...  
Keyword(s):  
Cell Morphology ◽  
Natural Environments ◽  
Marine Habitat ◽  
Alternative Mode ◽  
Surface Attachment ◽  
Cell Groups ◽  
Filamentous Cell ◽  
Bacterial Fitness ◽  
Structured Groups

Collective behavior in spatially structured groups, or biofilms, is the norm among microbes in their natural environments. Though biofilm formation has been studied for decades, tracing the mechanistic and ecological links between individual cell morphologies and the emergent features of cell groups is still in its infancy. Here we use single-cell–resolution confocal microscopy to explore biofilms of the human pathogenVibrio choleraein conditions mimicking its marine habitat. Prior reports have noted the occurrence of cellular filamentation inV. cholerae, with variable propensity to filament among both toxigenic and nontoxigenic strains. Using a filamenting strain ofV. choleraeO139, we show that cells with this morphotype gain a profound competitive advantage in colonizing and spreading on particles of chitin, the material many marineVibriospecies depend on for growth in seawater. Furthermore, filamentous cells can produce biofilms that are independent of primary secreted components of theV. choleraebiofilm matrix; instead, filamentous biofilm architectural strength appears to derive at least in part from the entangled mesh of cells themselves. The advantage gained by filamentous cells in early chitin colonization and growth is countered in long-term competition experiments with matrix-secretingV. choleraevariants, whose densely packed biofilm structures displace competitors from surfaces. Overall, our results reveal an alternative mode of biofilm architecture that is dependent on filamentous cell morphology and advantageous in environments with rapid chitin particle turnover. This insight provides an environmentally relevant example of how cell morphology can impact bacterial fitness.

Two repetitive, biofilm-forming proteins from Staphylococci: from disorder to extension

2015 ◽  
Vol 43 (5) ◽  
pp. 861-866 ◽  
Author(s):  
Fiona Whelan ◽  
Jennifer R. Potts
Keyword(s):  
Medical Device ◽  
Staphylococcus Epidermidis ◽  
Molecular Mechanisms ◽  
Surface Proteins ◽  
Initial Surface ◽  
Surface Attachment ◽  
Bacterial Surface ◽  
Host Interactions ◽  
And Function

Staphylococcus aureus and Staphylococcus epidermidis are an important cause of medical device-related infections that are difficult to treat with antibiotics. Biofilms, in which bacteria are embedded in a bacterially-produced exopolymeric matrix, form on the surface of the implanted medical device. Our understanding of the molecular mechanisms underlying the initial surface attachment and subsequent intercellular interactions as the biofilm matures is improving. Biofilm accumulation can be mediated by a partially deacetylated form of poly-N-acetylglucosamine (PNAG) but, more recently, the role of bacterial surface proteins is being recognized. Here we describe the structure and function of two S. aureus cell surface proteins, FnBPA and SasG, implicated in host interactions and biofilm accumulation. These multifunctional proteins employ intrinsic disorder for distinct molecular outcomes. In the case of FnBPA, disorder generates adhesive arrays that bind fibronectin (Fn); in the case of SasG, disorder is, counterintuitively, used to maintain a strong extended fold.

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 Red deer (Cervus elaphus) Did Not Play the Role of Maintenance Host for Bluetongue Virus in France: The Burden of Proof by Long-Term Wildlife Monitoring and Culicoides Snapshots

Viruses ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 903 ◽  
Author(s):  
Sophie Rossi ◽  
Thomas Balenghien ◽  
Cyril Viarouge ◽  
Eva Faure ◽  
Gina Zanella ◽  
...  
Keyword(s):  
Cervus Elaphus ◽  
Bluetongue Virus ◽  
Red Deer ◽  
Feeding Habits ◽  
Burden Of Proof ◽  
Natural Environments ◽  
Sylvatic Cycle ◽  
Bridge Species

Bluetongue virus (BTV) is a Culicoides-borne pathogen infecting both domestic and wild ruminants. In Europe, the Red Deer (Cervus elaphus) (RD) is considered a potential BTV reservoir, but persistent sylvatic cycle has not yet been demonstrated. In this paper, we explored the dynamics of BTV1 and BTV8 serotypes in the RD in France, and the potential role of that species in the re-emergence of BTV8 in livestock by 2015 (i.e., 5 years after the former last domestic cases). We performed 8 years of longitudinal monitoring (2008–2015) among 15 RD populations and 3065 individuals. We compared Culicoides communities and feeding habits within domestic and wild animal environments (51,380 samples). Culicoides diversity (>30 species) varied between them, but bridge-species able to feed on both wild and domestic hosts were abundant in both situations. Despite the presence of competent vectors in natural environments, BTV1 and BTV8 strains never spread in RD along the green corridors out of the domestic outbreak range. Decreasing antibody trends with no PCR results two years after the last domestic outbreak suggests that seropositive young RD were not recently infected but carried maternal antibodies. We conclude that RD did not play a role in spreading or maintaining BTV in France.

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 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.

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