scholarly journals Non-motile subpopulations of Pseudomonas aeruginosa repress flagellar motility in motile cells through a type IV pili- and Pel-dependent mechanism

2021 ◽  
Author(s):  
Kimberley A. Lewis ◽  
Danielle M Vermilyea ◽  
Shanice S Webster ◽  
Jaime de Anda ◽  
Gerard Wong ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Total Population ◽  
Type Iv Pili ◽  
External Factors ◽  
Flagellar Motility ◽  
Wild Type ◽  
Type Iv ◽  
Motile Cells ◽  
Flagellum Biosynthesis ◽  
Dependent Mechanism

The downregulation of P. aeruginosa flagellar motility is a key event in biofilm formation, host-colonization, and the formation of microbial communities, but the external factors that repress motility are not well understood. Here, we report that under swarming conditions, motility can be repressed by cells that are non-motile due to the absence of a flagellum or flagellar rotation. Non-motile cells, due to mutations that prevent either flagellum biosynthesis or rotation, present at 5% of the total population suppressed swarming of wild-type cells under the conditions tested in this study. Non-motile cells required functional type IV pili and the ability to produce the Pel exopolysaccharide to suppress swarming by the motile wild type. In contrast, motile cells required only type IV pili, but not Pel production, in order for swarming to be repressed by non-motile cells. We hypothesize that interactions between motile and non-motile cells may enhance the formation of sessile communities including those involving multiple genotypes, phenotypically-diverse cells, and perhaps other species.

scholarly journals Biofilm formation by Pseudomonas aeruginosa wild type, flagella and type IV pili mutants

2003 ◽  
Vol 48 (6) ◽  
pp. 1511-1524 ◽  
Author(s):  
Mikkel Klausen ◽  
Arne Heydorn ◽  
Paula Ragas ◽  
Lotte Lambertsen ◽  
Anders Aaes-Jørgensen ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Type Iv Pili ◽  
Wild Type ◽  
Type Iv

scholarly journals Type IV Pili Are Required for Virulence, Twitching Motility, and Biofilm Formation of Acidovorax avenae subsp. citrulli

2009 ◽  
Vol 22 (8) ◽  
pp. 909-920 ◽  
Author(s):  
Ofir Bahar ◽  
Tal Goffer ◽  
Saul Burdman
Keyword(s):  
Biofilm Formation ◽  
Host Plants ◽  
Seed Transmission ◽  
Type Iv Pili ◽  
Twitching Motility ◽  
Wild Type ◽  
Type Iv ◽  
Group I ◽  
Tn5 Mutant

Acidovorax avenae subsp. citrulli is the causal agent of bacterial fruit blotch (BFB), a threatening disease of watermelon, melon, and other cucurbits. Despite the economic importance of BFB, relatively little is known about basic aspects of the pathogen's biology and the molecular basis of its interaction with host plants. To identify A. avenae subsp. citrulli genes associated with pathogenicity, we generated a transposon (Tn5) mutant library on the background of strain M6, a group I strain of A. avenae subsp. citrulli, and screened it for reduced virulence by seed-transmission assays with melon. Here, we report the identification of a Tn5 mutant with reduced virulence that is impaired in pilM, which encodes a protein involved in assembly of type IV pili (TFP). Further characterization of this mutant revealed that A. avenae subsp. citrulli requires TFP for twitching motility and wild-type levels of biofilm formation. Significant reductions in virulence and biofilm formation as well as abolishment of twitching were also observed in insertional mutants affected in other TFP genes. We also provide the first evidence that group I strains of A. avenae subsp. citrulli can colonize and move through host xylem vessels.

scholarly journals Regulation of Type IV Pili Contributes to Surface Behaviors of Historical and Epidemic Strains of Clostridium difficile

2015 ◽  
Vol 198 (3) ◽  
pp. 565-577 ◽  
Author(s):  
Erin B. Purcell ◽  
Robert W. McKee ◽  
Eric Bordeleau ◽  
Vincent Burrus ◽  
Rita Tamayo
Keyword(s):  
Clostridium Difficile ◽  
Biofilm Formation ◽  
The United States ◽  
Type Iv Pili ◽  
Flagellar Motility ◽  
Content Type ◽  
Type Iv ◽  
Intestinal Pathogen ◽  
Surface Motility ◽  
Pilin Gene

ABSTRACTThe intestinal pathogenClostridium difficileis an urgent public health threat that causes antibiotic-associated diarrhea and is a leading cause of fatal nosocomial infections in the United States.C. difficilerates of recurrence and mortality have increased in recent years due to the emergence of so-called “hypervirulent” epidemic strains. A great deal of the basic biology ofC. difficilehas not been characterized. Recent findings that flagellar motility, toxin synthesis, and type IV pilus (TFP) formation are regulated by cyclic diguanylate (c-di-GMP) reveal the importance of this second messenger forC. difficilegene regulation. However, the function(s) of TFP inC. difficileremains largely unknown. Here, we examine TFP-dependent phenotypes and the role of c-di-GMP in controlling TFP production in the historical 630 and epidemic R20291 strains ofC. difficile. We demonstrate that TFP contribute toC. difficilebiofilm formation in both strains, but with a more prominent role in R20291. Moreover, we report that R20291 is capable of TFP-dependent surface motility, which has not previously been described inC. difficile. The expression and regulation of thepilA1pilin gene differs between R20291 and 630, which may underlie the observed differences in TFP-mediated phenotypes. The differences inpilA1expression are attributable to greater promoter-driven transcription in R20291. In addition, R20291, but not 630, upregulates c-di-GMP levels during surface-associated growth, suggesting that the bacterium senses its substratum. The differential regulation of surface behaviors in historical and epidemicC. difficilestrains may contribute to the different infection outcomes presented by these strains.IMPORTANCEHowClostridium difficileestablishes and maintains colonization of the host bowel is poorly understood. Surface behaviors ofC. difficileare likely relevant during infection, representing possible interactions between the bacterium and the intestinal environment. Pili mediate bacterial interactions with various surfaces and contribute to the virulence of many pathogens. We report that type IV pili (TFP) contribute to biofilm formation byC. difficile. TFP are also required for surface motility, which has not previously been demonstrated forC. difficile. Furthermore, an epidemic-associatedC. difficilestrain showed higher pilin gene expression and greater dependence on TFP for biofilm production and surface motility. Differences in TFP regulation and their effects on surface behaviors may contribute to increased virulence in recent epidemic strains.

scholarly journals Motility-Independent Formation of Antibiotic-TolerantPseudomonas aeruginosaAggregates

2019 ◽  
Vol 85 (14) ◽  
Author(s):  
Sally Demirdjian ◽  
Hector Sanchez ◽  
Daniel Hopkins ◽  
Brent Berwin
Keyword(s):  
Biofilm Formation ◽  
Bacterial Pathogen ◽  
Aggregate Formation ◽  
Flagellar Motility ◽  
Wild Type ◽  
Chronic Infections ◽  
Content Type ◽  
Temporal Adaptation ◽  
Bacterial Aggregates

ABSTRACTPseudomonas aeruginosais a bacterial pathogen that causes severe chronic infections in immunocompromised individuals. This bacterium is highly adaptable to its environments, which frequently select for traits that promote bacterial persistence. A clinically significant temporal adaptation is the formation of surface- or cell-adhered bacterial biofilms that are associated with increased resistance to immune and antibiotic clearance. Extensive research has shown that bacterial flagellar motility promotes formation of such biofilms, whereupon the bacteria subsequently become nonmotile. However, recent evidence shows that antibiotic-tolerant nonattached bacterial aggregates, distinct from surface-adhered biofilms, can form, and these have been reported in the context of lung infections, otitis media, nonhealing wounds, and soft tissue fillers. It is unclear whether the same bacterial traits are required for aggregate formation as for biofilm formation. In this report, using isogenic mutants, we demonstrate thatP. aeruginosaaggregates in liquid cultures are spontaneously formed independent of bacterial flagellar motility and independent of an exogenous scaffold. This contrasts with the role of the flagellum to initiate surface-adhered biofilms. Similarly to surface-attached biofilms, these aggregates exhibit increased antibiotic tolerance compared to planktonic cultures. These findings provide key insights into the requirements for aggregate formation that contrast with those for biofilm formation and that may have relevance for the persistence and dissemination of nonmotile bacteria found within chronic clinical infections.IMPORTANCEIn this work, we have investigated the role of bacterial motility with regard to antibiotic-tolerant bacterial aggregate formation. Previous work has convincingly demonstrated thatP. aeruginosaflagellar motility promotes the formation of surface-adhered biofilms in many systems. In contrast, aggregate formation byP. aeruginosawas observed for nonmotile but not for motile cells in the presence of an exogenous scaffold. Here, we demonstrate that both wild-typeP. aeruginosaand mutants that genetically lack motility spontaneously form antibiotic-tolerant aggregates in the absence of an exogenously added scaffold. Additionally, we also demonstrate that wild-type (WT) and nonmotileP. aeruginosabacteria can coaggregate, shedding light on potential physiological interactions and heterogeneity of aggregates.

scholarly journals Axenic Biofilm Formation and Aggregation bySynechocystissp. Strain PCC 6803 Are Induced by Changes in Nutrient Concentration and Require Cell Surface Structures

2019 ◽  
Vol 85 (7) ◽  
Author(s):  
Rey Allen ◽  
Bruce E. Rittmann ◽  
Roy Curtiss
Keyword(s):  
Biofilm Formation ◽  
Molecular Mechanisms ◽  
Type Iv Pili ◽  
Biofuel Production ◽  
Oxygenic Photosynthesis ◽  
Phototrophic Biofilm ◽  
Bg11 Medium ◽  
Phototrophic Biofilms ◽  
Type Iv ◽  
Cell Surface Structures

ABSTRACTPhototrophic biofilms are key to nutrient cycling in natural environments and bioremediation technologies, but few studies describe biofilm formation by pure (axenic) cultures of a phototrophic microbe. The cyanobacteriumSynechocystissp. strain PCC 6803 (hereSynechocystis) is a model microorganism for the study of oxygenic photosynthesis and biofuel production. We report here that wild-type (WT)Synechocystiscaused extensive biofilm formation in a 2,000-liter outdoor nonaxenic photobioreactor under conditions attributed to nutrient limitation. We developed a biofilm assay and found that axenicSynechocystisforms biofilms of cells and extracellular material but only when cells are induced by an environmental signal, such as a reduction in the concentration of growth medium BG11. Mutants lacking cell surface structures, namely type IV pili and the S-layer, do not form biofilms. To further characterize the molecular mechanisms of cell-cell binding bySynechocystis, we also developed a rapid (8-h) axenic aggregation assay. Mutants lacking type IV pili were unable to aggregate, but mutants lacking a homolog to Wza, a protein required for type 1 exopolysaccharide export inEscherichia coli, had a superbinding phenotype. In WT cultures, 1.2× BG11 medium induced aggregation to the same degree as 0.8× BG11 medium. Overall, our data support that Wza-dependent exopolysaccharide is essential to maintain stable, uniform suspensions of WTSynechocystiscells in unmodified growth medium and that this mechanism is counteracted in a pilus-dependent manner under altered BG11 concentrations.IMPORTANCEMicrobes can exist as suspensions of individual cells in liquids and also commonly form multicellular communities attached to surfaces. Surface-attached communities, called biofilms, can confer antibiotic resistance to pathogenic bacteria during infections and establish food webs for global nutrient cycling in the environment. Phototrophic biofilm formation is one of the earliest phenotypes visible in the fossil record, dating back over 3 billion years. Despite the importance and ubiquity of phototrophic biofilms, most of what we know about the molecular mechanisms, genetic regulation, and environmental signals of biofilm formation comes from studies of heterotrophic bacteria. We aim to help bridge this knowledge gap by developing new assays forSynechocystis, a phototrophic cyanobacterium used to study oxygenic photosynthesis and biofuel production. With the aid of these new assays, we contribute to the development ofSynechocystisas a model organism for the study of axenic phototrophic biofilm formation.

scholarly journals Type IV pili promote early biofilm formation byClostridium difficile

2016 ◽  
Vol 74 (6) ◽  
pp. ftw061 ◽  
Author(s):  
Grace A. Maldarelli ◽  
Kurt H. Piepenbrink ◽  
Alison J. Scott ◽  
Jeffrey A. Freiberg ◽  
Yang Song ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Type Iv Pili ◽  
Type Iv

scholarly journals Hik36–Hik43 and Rre6 act as a two-component regulatory system to control cell aggregation in Synechocystis sp. PCC6803

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Kota Kera ◽  
Yuichiro Yoshizawa ◽  
Takehiro Shigehara ◽  
Tatsuya Nagayama ◽  
Masaru Tsujii ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Morphological Changes ◽  
Response Regulator ◽  
Control Cell ◽  
Regulatory System ◽  
Cell Aggregation ◽  
Wild Type ◽  
Type Iv ◽  
Two Component ◽  
In The Wild

Abstract In response to environmental stress the model cyanobacterium, Synechocystis sp. PCC6803 can switch from a planktonic state to autoaggregation and biofilm formation. The precise mechanism of this transition remains unknown. Here we investigated the role of a candidate two-component regulatory system (TCS) in controlling morphological changes, as a way to understand the intermediate molecular steps that are part of the signaling pathway. A bacterial two-hybrid assay showed that the response regulator Rre6 formed a TCS together with a split histidine kinase consisting of Hik36 and Hik43. Individual disruption mutants displayed autoaggregation in a static culture. In contrast, unlike in the wild type, high salinity did not induce biofilm formation in Δhik36, Δhik43 and Δrre6. The expression levels of exopolysaccharide (EPS) production genes were higher in Δhik36 and Δhik43, compared with the wild type, but lower in Δrre6, suggesting that the TCS regulated EPS production in Synechocystis. Rre6 interacted physically with the motor protein PilT2, that is a component of the type IV pilus system. This interaction was enhanced in a phosphomimic version of Rre6. Taken together, Hik36–Hik43–Rre6 function as an upstream component of the pili-related signal transduction cascade and control the prevention of cell adhesion and biofilm formation.

scholarly journals DNA Binding: a Novel Function of Pseudomonas aeruginosa Type IV Pili

2005 ◽  
Vol 187 (4) ◽  
pp. 1455-1464 ◽  
Author(s):  
Erin J. van Schaik ◽  
Carmen L. Giltner ◽  
Gerald F. Audette ◽  
David W. Keizer ◽  
Daisy L. Bautista ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Dna Binding ◽  
Biofilm Formation ◽  
Quaternary Structure ◽  
Natural Transformation ◽  
Ex Vivo ◽  
Specific Binding ◽  
Type Iv Pili ◽  
Type Iv ◽  
Bacteriophage Infection

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa produces multifunctional, polar, filamentous appendages termed type IV pili. Type IV pili are involved in colonization during infection, twitching motility, biofilm formation, bacteriophage infection, and natural transformation. Electrostatic surface analysis of modeled pilus fibers generated from P. aeruginosa strain PAK, K122-4, and KB-7 pilin monomers suggested that a solvent-exposed band of positive charge may be a common feature of all type IV pili. Several functions of type IV pili, including natural transformation and biofilm formation, involve DNA. We investigated the ability of P. aeruginosa type IV pili to bind DNA. Purified PAK, K122-4, and KB-7 pili were observed to bind both bacterial plasmid and salmon sperm DNA in a concentration-dependent and saturable manner. PAK pili had the highest affinity for DNA, followed by K122-4 and KB-7 pili. DNA binding involved backbone interactions and preferential binding to pyrimidine residues even though there was no evidence of sequence-specific binding. Pilus-mediated DNA binding was a function of the intact pilus and thus required elements present in the quaternary structure. However, binding also involved the pilus tip as tip-specific, but not base-specific, antibodies inhibited DNA binding. The conservation of a Thr residue in all type IV pilin monomers examined to date, along with the electrostatic data, implies that DNA binding is a conserved function of type IV pili. Pilus-mediated DNA binding could be important for biofilm formation both in vivo during an infection and ex vivo on abiotic surfaces.

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