Ecological Advantages of Autolysis during the Development and Dispersal of Pseudoalteromonas tunicata Biofilms

ABSTRACT In the ubiquitous marine bacterium Pseudoalteromonas tunicata, subpopulations of cells are killed by the production of an autocidal protein, AlpP, during biofilm development. Our data demonstrate an involvement of this process in two parameters, dispersal and phenotypic diversification, which are of importance for the ecology of this organism and for its survival within the environment. Cell death in P. tunicata wild-type biofilms led to a major reproducible dispersal event after 192 h of biofilm development. The dispersal was not observed with a ΔAlpP mutant strain. Using flow cytometry and the fluorescent dye DiBAC4(3), we also show that P. tunicata wild-type cells that disperse from biofilms have enhanced metabolic activity compared to those cells that disperse from ΔAlpP mutant biofilms, possibly due to nutrients released from dead cells. Furthermore, we report that there was considerable phenotypic variation among cells dispersing from wild-type biofilms but not from the ΔAlpP mutant. Wild-type cells that dispersed from biofilms showed significantly increased variations in growth, motility, and biofilm formation, which may be important for successful colonization of new surfaces. These findings suggest for the first time that the autocidal events mediated by an antibacterial protein can confer ecological advantages to the species by generating a metabolically active and phenotypically diverse subpopulation of dispersal cells.

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Altering the Ratio of Phenazines in Pseudomonas chlororaphis (aureofaciens) Strain 30-84: Effects on Biofilm Formation and Pathogen Inhibition

Journal of Bacteriology ◽

10.1128/jb.01587-07 ◽

2008 ◽

Vol 190 (8) ◽

pp. 2759-2766 ◽

Cited By ~ 91

Author(s):

V. S. R. K. Maddula ◽

E. A. Pierson ◽

L. S. Pierson

Keyword(s):

Fungal Pathogen ◽

Biofilm Formation ◽

Flow Cell ◽

Gaeumannomyces Graminis ◽

Pseudomonas Chlororaphis ◽

Wild Type ◽

Initial Attachment ◽

Pathogen Inhibition ◽

Biofilm Development ◽

Derivatives Of

ABSTRACT Pseudomonas chlororaphis strain 30-84 is a plant-beneficial bacterium that is able to control take-all disease of wheat caused by the fungal pathogen Gaeumannomyces graminis var. tritici. The production of phenazines (PZs) by strain 30-84 is the primary mechanism of pathogen inhibition and contributes to the persistence of strain 30-84 in the rhizosphere. PZ production is regulated in part by the PhzR/PhzI quorum-sensing (QS) system. Previous flow cell analyses demonstrated that QS and PZs are involved in biofilm formation in P. chlororaphis (V. S. R. K. Maddula, Z. Zhang, E. A. Pierson, and L. S. Pierson III, Microb. Ecol. 52:289-301, 2006). P. chlororaphis produces mainly two PZs, phenazine-1-carboxylic acid (PCA) and 2-hydroxy-PCA (2-OH-PCA). In the present study, we examined the effect of altering the ratio of PZs produced by P. chlororaphis on biofilm formation and pathogen inhibition. As part of this study, we generated derivatives of strain 30-84 that produced only PCA or overproduced 2-OH-PCA. Using flow cell assays, we found that these PZ-altered derivatives of strain 30-84 differed from the wild type in initial attachment, mature biofilm architecture, and dispersal from biofilms. For example, increased 2-OH-PCA production promoted initial attachment and altered the three-dimensional structure of the mature biofilm relative to the wild type. Additionally, both alterations promoted thicker biofilm development and lowered dispersal rates compared to the wild type. The PZ-altered derivatives of strain 30-84 also differed in their ability to inhibit the fungal pathogen G. graminis var. tritici. Loss of 2-OH-PCA resulted in a significant reduction in the inhibition of G. graminis var. tritici. Our findings suggest that alterations in the ratios of antibiotic secondary metabolites synthesized by an organism may have complex and wide-ranging effects on its biology.

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Quorum Sensing Influences Burkholderia thailandensis Biofilm Development and Matrix Production

Journal of Bacteriology ◽

10.1128/jb.00047-16 ◽

2016 ◽

Vol 198 (19) ◽

pp. 2643-2650 ◽

Cited By ~ 23

Author(s):

Boo Shan Tseng ◽

Charlotte D. Majerczyk ◽

Daniel Passos da Silva ◽

Josephine R. Chandler ◽

E. Peter Greenberg ◽

...

Keyword(s):

Quorum Sensing ◽

Biofilm Formation ◽

Bacterial Species ◽

Matrix Material ◽

Close Relative ◽

Wild Type ◽

Flow Conditions ◽

Burkholderia Thailandensis ◽

Content Type ◽

Biofilm Development

ABSTRACTMembers of the genusBurkholderiaare known to be adept at biofilm formation, which presumably assists in the survival of these organisms in the environment and the host. Biofilm formation has been linked to quorum sensing (QS) in several bacterial species. In this study, we characterizedBurkholderia thailandensisbiofilm development under flow conditions and sought to determine whether QS contributes to this process.B. thailandensisbiofilm formation exhibited an unusual pattern: the cells formed small aggregates and then proceeded to produce mature biofilms characterized by “dome” structures filled with biofilm matrix material. We showed that this process was dependent on QS.B. thailandensishas three acyl-homoserine lactone (AHL) QS systems (QS-1, QS-2, and QS-3). An AHL-negative strain produced biofilms consisting of cell aggregates but lacking the matrix-filled dome structures. This phenotype was rescued via exogenous addition of the three AHL signals. Of the threeB. thailandensisQS systems, we show that QS-1 is required for proper biofilm development, since abtaR1mutant, which is defective in QS-1 regulation, forms biofilms without these dome structures. Furthermore, our data show that the wild-type biofilm biomass, as well as the material inside the domes, stains with a fucose-binding lectin. ThebtaR1mutant biofilms, however, are negative for fucose staining. This suggests that the QS-1 system regulates the production of a fucose-containing exopolysaccharide in wild-type biofilms. Finally, we present data showing that QS ability during biofilm development produces a biofilm that is resistant to dispersion under stress conditions.IMPORTANCEThe saprophyteBurkholderia thailandensisis a close relative of the pathogenic bacteriumBurkholderia pseudomallei, the causative agent of melioidosis, which is contracted from its environmental reservoir. Since most bacteria in the environment reside in biofilms,B. thailandensisis an ideal model organism for investigating questions inBurkholderiaphysiology. In this study, we characterizedB. thailandensisbiofilm development and sought to determine if quorum sensing (QS) contributes to this process. Our work shows thatB. thailandensisproduces biofilms with unusual dome structures under flow conditions. Our findings suggest that these dome structures are filled with a QS-regulated, fucose-containing exopolysaccharide that may be involved in the resilience ofB. thailandensisbiofilms against changes in the nutritional environment.

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AbaM Regulates Quorum Sensing, Biofilm Formation and Virulence in Acinetobacter baumannii

Journal of Bacteriology ◽

10.1128/jb.00635-20 ◽

2021 ◽

Author(s):

Mario López-Martín ◽

Jean-Frédéric Dubern ◽

Morgan R. Alexander ◽

Paul Williams

Keyword(s):

Quorum Sensing ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Plant Pathogens ◽

Galleria Mellonella ◽

Homoserine Lactone ◽

Infection Model ◽

Wild Type ◽

Surface Motility ◽

Biofilm Development

Acinetobacter baumannii possesses a single divergent luxR/luxI-type quorum sensing (QS) locus named abaR/abaI. This locus also contains a third gene located between abaR and abaI which we term abaM that codes for an uncharacterized member of the RsaM protein family known to regulate N-acylhomoserine lactone (AHL) dependent QS in other β- and γ-proteobacteria. Here we show that disruption of abaM via a T26 insertion in A. baumannii strain AB5075 resulted in increased production of N-(3-hydroxydodecanoyl)-L-homoserine lactone (OHC12) and enhanced surface motility and biofilm formation. In contrast to the wild type and abaI::T26 mutant, the virulence of the abaM::T26 mutant was completely attenuated in a Galleria mellonella infection model. Transcriptomic analysis of the abaM::T26 mutant revealed that AbaM differentially regulates at least 76 genes including the csu pilus operon and the acinetin 505 lipopeptide biosynthetic operon, that are involved in surface adherence, biofilm formation and virulence. A comparison of the wild type, abaM::T26 and abaI::T26 transcriptomes, indicates that AbaM regulates ∼21% of the QS regulon including the csu operon. Moreover, the QS genes (abaI/abaR) were among the most upregulated in the abaM::T26 mutant. A. baumannii lux-based abaM reporter gene fusions revealed that abaM expression is positively regulated by QS but negatively auto-regulated. Overall, the data presented in this work demonstrates that AbaM plays a central role in regulating A. baumannii QS, virulence, surface motility and biofilm formation. Importance Acinetobacter baumanni is a multi-antibiotic resistant pathogen of global healthcare importance. Understanding Acinetobacter virulence gene regulation could aid the development of novel anti-infective strategies. In A. baumannii, the abaR and abaI genes that code for the receptor and synthase components of an N-acylhomoserine (AHL) lactone-dependent quorum sensing system (QS) are separated by abaM. Here we show that although mutation of abaM increased AHL production, surface motility and biofilm development, it resulted in the attenuation of virulence. AbaM was found to control both QS-dependent and QS-independent genes. The significance of this work lies in the identification of AbaM, an RsaM ortholog known to control virulence in plant pathogens, as a modulator of virulence in a human pathogen.

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Novel Role for the Streptococcus pneumoniae Toxin Pneumolysin in the Assembly of Biofilms

mBio ◽

10.1128/mbio.00655-13 ◽

2013 ◽

Vol 4 (5) ◽

Cited By ~ 39

Author(s):

Joshua R. Shak ◽

Herbert P. Ludewick ◽

Kristen E. Howery ◽

Fuminori Sakai ◽

Hong Yi ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Hemolytic Activity ◽

Biofilm Formation ◽

Early Time ◽

Wild Type ◽

Knockout Mutant ◽

Content Type ◽

Biofilm Development ◽

Almost All

ABSTRACTStreptococcus pneumoniaeis an important commensal and pathogen responsible for almost a million deaths annually in children under five. The formation of biofilms byS. pneumoniaeis important in nasopharyngeal colonization, pneumonia, and otitis media. Pneumolysin (Ply) is a toxin that contributes significantly to the virulence ofS. pneumoniaeand is an important candidate as a serotype-independent vaccine target. Having previously demonstrated that aluxSknockout mutant was unable to form early biofilms and expressed lessplymRNA than the wild type, we conducted a study to investigate the role of Ply in biofilm formation. We found that Ply was expressed in early phases of biofilm development and localized to cellular aggregates as early as 4 h postinoculation.S. pneumoniae plyknockout mutants in D39 and TIGR4 backgrounds produced significantly less biofilm biomass than wild-type strains at early time points, both on polystyrene and on human respiratory epithelial cells, cultured under static or continuous-flow conditions. Ply’s role in biofilm formation appears to be independent of its hemolytic activity, asS. pneumoniaeserotype 1 strains, which produce a nonhemolytic variant of Ply, were still able to form biofilms. Transmission electron microscopy of biofilms grown on A549 lung cells using immunogold demonstrated that Ply was located both on the surfaces of pneumococcal cells and in the extracellular biofilm matrix. Altogether, our studies demonstrate a novel role for pneumolysin in the assembly ofS. pneumoniaebiofilms that is likely important during both carriage and disease and therefore significant for pneumolysin-targeting vaccines under development.IMPORTANCEThe bacteriumStreptococcus pneumoniae(commonly known as the pneumococcus) is commonly carried in the human nasopharynx and can spread to other body sites to cause disease. In the nasopharynx, middle ear, and lungs, the pneumococcus forms multicellular surface-associated structures called biofilms. Pneumolysin is an important toxin produced by almost allS. pneumoniaestrains, extensively studied for its ability to cause damage to human tissue. In this paper, we demonstrate that pneumolysin has a previously unrecognized role in biofilm formation by showing that strains without pneumolysin are unable to form the same amount of biofilm on plastic and human cell substrates. Furthermore, we show that the role of pneumolysin in biofilm formation is separate from the hemolytic activity responsible for tissue damage during pneumococcal diseases. This novel role for pneumolysin suggests that pneumococcal vaccines directed against this protein should be investigated for their potential impact on biofilms formed during carriage and disease.

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Biofilm Formation by Moraxella catarrhalis In Vitro: Roles of the UspA1 Adhesin and the Hag Hemagglutinin

Infection and Immunity ◽

10.1128/iai.74.3.1588-1596.2006 ◽

2006 ◽

Vol 74 (3) ◽

pp. 1588-1596 ◽

Cited By ~ 59

Author(s):

Melanie M. Pearson ◽

Cassie A. Laurence ◽

Sarah E. Guinn ◽

Eric J. Hansen

Keyword(s):

Crystal Violet ◽

Moraxella Catarrhalis ◽

Biofilm Formation ◽

Transposon Mutagenesis ◽

Nucleotide Sequence Analysis ◽

Wild Type ◽

Chromosomal Dna ◽

Negative Effect ◽

Biofilm Development

ABSTRACT Mutant analysis was used to identify Moraxella catarrhalis gene products necessary for biofilm development in a crystal violet-based assay involving 24-well tissue culture plates. The wild-type M. catarrhalis strains that formed the most extensive biofilms in this system proved to be refractory to transposon mutagenesis, so an M. catarrhalis strain was constructed that was both able to form biofilms in vitro and amenable to transposon mutagenesis. Chromosomal DNA from the biofilm-positive strain O46E was used to transform the biofilm-negative strain O35E; transformants able to form biofilms were identified and subjected to transposon-mediated mutagenesis. Biofilm-negative mutants of these transformants were shown to have a transposon insertion in the uspA1 gene. Nucleotide sequence analysis revealed that the biofilm-positive transformant T14 contained a hybrid O46E-O35E uspA1 gene, with the N-terminal 155 amino acids being derived from the O46E UspA1 protein. Transformant T14 was also shown to be unable to express the Hag protein, which normally extends from the surface of the M. catarrhalis cell. Introduction of a wild-type O35E hag gene into T14 eliminated its ability to form a biofilm. When the hybrid O46E-O35E uspA1 gene from T14 was used to replace the uspA1 gene of O35E, this transformant strain did not form a biofilm. However, inactivation of the hag gene did allow biofilm formation by strain O35E expressing the hybrid O46E-O35E uspA1 gene product. The Hag protein was shown to have an inhibitory or negative effect on biofilm formation by these M. catarrhalis strains in the crystal violet-based assay.

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O-Mannosylation in Candida albicans Enables Development of Interkingdom Biofilm Communities

mBio ◽

10.1128/mbio.00911-14 ◽

2014 ◽

Vol 5 (2) ◽

Cited By ~ 41

Author(s):

Lindsay C. Dutton ◽

Angela H. Nobbs ◽

Katy Jepson ◽

Mark A. Jepson ◽

M. Margaret Vickerman ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Biofilm Formation ◽

Early Stage ◽

Growth Conditions ◽

Wild Type ◽

Content Type ◽

Subsequent Performance ◽

Biofilm Development ◽

Mutant Cells

ABSTRACTCandida albicansis a fungus that colonizes oral cavity surfaces, the gut, and the genital tract.Streptococcus gordoniiis a ubiquitous oral bacterium that has been shown to form biofilm communities withC. albicans. Formation of dual-speciesS. gordonii-C. albicansbiofilm communities involves interaction of theS. gordoniiSspB protein with the Als3 protein on the hyphal filament surface ofC. albicans. Mannoproteins comprise a major component of theC. albicanscell wall, and in this study we sought to determine if mannosylation in cell wall biogenesis ofC. albicanswas necessary for hyphal adhesin functions associated with interkingdom biofilm development. AC. albicans mnt1Δmnt2Δ mutant, with deleted α-1,2-mannosyltransferase genes and thus defective inO-mannosylation, was abrogated in biofilm formation under various growth conditions and produced hyphal filaments that were not recognized byS. gordonii. Cell wall proteomes of hypha-formingmnt1Δmnt2Δ mutant cells showed growth medium-dependent alterations, compared to findings for the wild type, in a range of protein components, including Als1, Als3, Rbt1, Scw1, and Sap9. Hyphal filaments formed bymnt1Δmnt2Δ mutant cells, unlike wild-type hyphae, did not interact withC. albicansAls3 or Hwp1 partner cell wall proteins or withS. gordoniiSspB partner adhesin, suggesting defective functionality of adhesins on themnt1Δmnt2Δ mutant. These observations imply that early stageO-mannosylation is critical for activation of hyphal adhesin functions required for biofilm formation, recognition by bacteria such asS. gordonii, and microbial community development.IMPORTANCEIn the human mouth, microorganisms form communities known as biofilms that adhere to the surfaces present.Candida albicansis a fungus that is often found within these biofilms. We have focused on the mechanisms by whichC. albicansbecomes incorporated into communities containing bacteria, such asStreptococcus. We find that impairment of early stage addition of mannose sugars toC. albicanshyphal filament proteins deleteriously affects their subsequent performance in mediating formation of polymicrobial biofilms. Our analyses provide new understanding of the way that microbial communities develop, and of potential means to controlC. albicansinfections.

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Enhanced Biofilm Formation and Loss of Capsule Synthesis: Deletion of a Putative Glycosyltransferase in Porphyromonas gingivalis

Journal of Bacteriology ◽

10.1128/jb.01685-05 ◽

2006 ◽

Vol 188 (15) ◽

pp. 5510-5523 ◽

Cited By ~ 76

Author(s):

Mary E. Davey ◽

Margaret J. Duncan

Keyword(s):

Porphyromonas Gingivalis ◽

Biofilm Formation ◽

Capsular Polysaccharide ◽

Sequence Similarity ◽

Opportunistic Pathogen ◽

Insertion Mutant ◽

Wild Type ◽

High Sequence Similarity ◽

Biofilm Development

ABSTRACT Periodontitis is a biofilm-mediated disease. Porphyromonas gingivalis is an obligate anaerobe consistently associated with severe manifestations of this disease. As an opportunistic pathogen, the ability to proliferate within and disseminate from subgingival biofilm (plaque) is central to its virulence. Here, we report the isolation of a P. gingivalis transposon insertion mutant altered in biofilm development and the reconstruction and characterization of this mutation in three different wild-type strains. The mutation responsible for the altered biofilm phenotype was in a gene with high sequence similarity (∼61%) to a glycosyltransferase gene. The gene is located in a region of the chromosome that includes up to 16 genes predicted to be involved in the synthesis and transport of capsular polysaccharide. The phenotype of the reconstructed mutation in all three wild-type backgrounds is that of enhanced biofilm formation. In addition, in strain W83, a strain that is encapsulated, the glycosyltransferase mutation resulted in a loss of capsule. Further experiments showed that the W83 mutant strain was more hydrophobic and exhibited increased autoaggregation. Our results indicate that we have identified a gene involved in capsular-polysaccharide synthesis in P. gingivalis and that the production of capsule prevented attachment and the initiation of in vitro biofilm formation on polystyrene microtiter plates.

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Forward Genetic Dissection of Biofilm Development byFusobacterium nucleatum: Novel Functions of Cell Division Proteins FtsX and EnvC

mBio ◽

10.1128/mbio.00360-18 ◽

2018 ◽

Vol 9 (2) ◽

Cited By ~ 10

Author(s):

Chenggang Wu ◽

Abu Amar Mohamed Al Mamun ◽

Truc Thanh Luong ◽

Bo Hu ◽

Jianhua Gu ◽

...

Keyword(s):

Electron Microscopy ◽

Cell Division ◽

Cell Surface ◽

Biofilm Formation ◽

Cell Biology ◽

Associated Factors ◽

Surface Dynamics ◽

Wild Type ◽

Content Type ◽

Biofilm Development

ABSTRACTFusobacterium nucleatumis a key member of the human oral biofilm. It is also implicated in preterm birth and colorectal cancer. To facilitate basic studies of fusobacterial virulence, we describe here a versatile transposon mutagenesis procedure and a pilot screen for mutants defective in biofilm formation. Out of 10 independent biofilm-defective mutants isolated, the affected genes included the homologs of theEscherichia colicell division proteins FtsX and EnvC, the electron transport protein RnfA, and four proteins with unknown functions. Next, a facile new gene deletion method demonstrated that nonpolar, in-frame deletion offtsXorenvCproduces viable bacteria that are highly filamentous due to defective cell division. Transmission electron and cryo-electron microscopy revealed that the ΔftsXand ΔenvCmutant cells remain joined with apparent constriction, and scanning electron microscopy (EM) uncovered a smooth cell surface without the microfolds present in wild-type cells. FtsX and EnvC proteins interact with each other as well as a common set of interacting partners, many with unknown function. Last, biofilm development is altered when cell division is blocked by MinC overproduction; however, unlike the phenotypes of ΔftsXand ΔenvCmutants, a weakly adherent biofilm is formed, and the wild-type rugged cell surface is maintained. Therefore, FtsX and EnvC may perform novel functions inFusobacteriumcell biology. This is the first report of an unbiased approach to uncover genetic determinants of fusobacterial biofilm development. It points to an intriguing link among cytokinesis, cell surface dynamics, and biofilm formation, whose molecular underpinnings remain to be elucidated.IMPORTANCELittle is known about the virulence mechanisms and associated factors inF. nucleatum, due mainly to the lack of convenient genetic tools for this organism. We employed two efficient genetic strategies to identifyF. nucleatumbiofilm-defective mutants, revealing FtsX and EnvC among seven biofilm-associated factors. Electron microscopy established cell division defects of the ΔftsXand ΔenvCmutants, accompanied with a smooth cell surface, unlike the microfold, rugged appearance of wild-type bacteria. Proteomic studies demonstrated that FtsX and EnvC interact with each other as well as a set of common and unique interacting proteins, many with unknown functions. Importantly, blocking cell division by MinC overproduction led to formation of a weakly adherent biofilm, without alteration of the wild-type cell surface. Thus, this work links cell division and surface dynamics to biofilm development and lays a foundation for future genetic and biochemical investigations of basic cellular processes in this clinically significant pathogen.

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TolC Promotes ExPEC Biofilm Formation and Curli Production in Response to Medium Osmolarity

BioMed Research International ◽

10.1155/2014/574274 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 9

Author(s):

Bo Hou ◽

Xian-Rong Meng ◽

Li-Yuan Zhang ◽

Chen Tan ◽

Hui Jin ◽

...

Keyword(s):

Biofilm Formation ◽

Wild Type ◽

High Osmolarity ◽

E Coli ◽

Surrounding Environment ◽

Medium Osmolarity ◽

Tolc Protein ◽

First Time ◽

Expec Strain

While a high osmolarity medium activates Cpx signaling and causes CpxR to represscsgDexpression, and efflux protein TolC protein plays an important role in biofilm formation inEscherichia coli,whether TolC also responds to an osmolarity change to regulate biofilm formation in extraintestinal pathogenicE. coli(ExPEC) remains unknown. In this study, we constructedΔtolCmutant and complement ExPEC strains to investigate the role of TolC in the retention of biofilm formation and curli production capability under different osmotic conditions. TheΔtolCmutant showed significantly decreased biofilm formation and lost the ability to produce curli fimbriae compared to its parent ExPEC strain PPECC42 when cultured in M9 medium or 1/2 M9 medium of increased osmolarity with NaCl or sucrose at 28°C. However, biofilm formation and curli production levels were restored to wild-type levels in theΔtolCmutant in 1/2 M9 medium. We propose for the first time that TolC protein is able to form biofilm even under high osmotic stress. Our findings reveal an interplay between the role of TolC in ExPEC biofilm formation and the osmolarity of the surrounding environment, thus providing guidance for the development of a treatment for ExPEC biofilm formation.

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Role ofrpoSin Escherichia coli O157:H7 Strain H32 Biofilm Development and Survival

Applied and Environmental Microbiology ◽

10.1128/aem.02149-12 ◽

2012 ◽

Vol 78 (23) ◽

pp. 8331-8339 ◽

Cited By ~ 16

Author(s):

Jessica R. Sheldon ◽

Mi-Sung Yim ◽

Jessica H. Saliba ◽

Wai-Hong Chung ◽

Kwok-Yin Wong ◽

...

Keyword(s):

Escherichia Coli ◽

Lake Water ◽

Biofilm Formation ◽

Survival Rates ◽

Confocal Scanning Laser Microscopy ◽

Wild Type ◽

Minimal Growth ◽

Content Type ◽

Biofilm Development

ABSTRACTThe protein RpoS is responsible for mediating cell survival during the stationary phase by conferring cell resistance to various stressors and has been linked to biofilm formation. In this study, the role of therpoSgene inEscherichia coliO157:H7 biofilm formation and survival in water was investigated. Confocal scanning laser microscopy of biofilms established on coverslips revealed a nutrient-dependent role ofrpoSin biofilm formation, where the biofilm biomass volume of therpoSmutant was 2.4- to 7.5-fold the size of itsrpoS+wild-type counterpart in minimal growth medium. The enhanced biofilm formation of therpoSmutant did not, however, translate to increased survival in sterile double-distilled water (ddH2O), filter-sterilized lake water, or unfiltered lake water. TherpoSmutant had an overall reduction of 3.10 and 5.30 log10in sterile ddH2O and filter-sterilized lake water, respectively, while only minor reductions of 0.53 and 0.61 log10in viable counts were observed for the wild-type form in the two media over a 13-day period, respectively. However, the survival rates of the detached biofilm-derivedrpoS+andrpoSmutant cells were comparable. Under the competitive stress conditions of unfiltered lake water, the advantage conferred by the presence ofrpoSwas lost, and both the wild-type and knockout forms displayed similar declines in viable counts. These results suggest thatrpoSdoes have an influence on both biofilm formation and survival ofE. coliO157:H7 and that the advantage conferred byrpoSis contingent on the environmental conditions.

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