Dataset Information

Impact of Salt and Nutrient Content on Biofilm Formation by Vibrio fischeri.

ABSTRACT: Vibrio fischeri, a marine bacterium and symbiont of the Hawaiian bobtail squid Euprymna scolopes, depends on biofilm formation for successful colonization of the squid's symbiotic light organ. Here, we investigated if culture conditions, such as nutrient and salt availability, affect biofilm formation by V. fischeri by testing the formation of wrinkled colonies on solid media. We found that V. fischeri forms colonies with more substantial wrinkling when grown on the nutrient-dense LBS medium containing NaCl relative to those formed on the more nutrient-poor, seawater-salt containing SWT medium. The presence of both tryptone and yeast extract was necessary for the production of "normal" wrinkled colonies; when grown on tryptone alone, the colonies displayed a divoting phenotype and were attached to the agar surface. We also found that the type and concentration of specific seawater salts influenced the timing of biofilm formation. Of the conditions assayed, wrinkled colony formation occurred earliest in LBS(-Tris) media containing 425 mM NaCl, 35 mM MgSO4, and 5 mM CaCl2. Pellicle formation, another measure of biofilm development, was also enhanced in these growth conditions. Therefore, both nutrient and salt availability contribute to V. fischeri biofilm formation. While growth was unaffected, these optimized conditions resulted in increased syp locus expression as measured by a PsypA-lacZ transcriptional reporter. We anticipate these studies will help us understand how the natural environment of V. fischeri affects its ability to form biofilms and, ultimately, colonize E. scolopes.

SUBMITTER: Marsden AE

PROVIDER: S-EPMC5266276 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Impact of Salt and Nutrient Content on Biofilm Formation by Vibrio fischeri.

Marsden Anne E AE Grudzinski Kevin K Ondrey Jakob M JM DeLoney-Marino Cindy R CR Visick Karen L KL

PloS one 20170125 1

Vibrio fischeri, a marine bacterium and symbiont of the Hawaiian bobtail squid Euprymna scolopes, depends on biofilm formation for successful colonization of the squid's symbiotic light organ. Here, we investigated if culture conditions, such as nutrient and salt availability, affect biofilm formation by V. fischeri by testing the formation of wrinkled colonies on solid media. We found that V. fischeri forms colonies with more substantial wrinkling when grown on the nutrient-dense LBS medium con ...[more]

PMID: 28122010

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Project description:Biofilms, complex communities of microorganisms surrounded by a self-produced matrix, facilitate attachment and provide protection to bacteria. A natural model used to study biofilm formation is the symbiosis between Vibrio fischeri and its host, the Hawaiian bobtail squid, Euprymna scolopes Host-relevant biofilm formation is a tightly regulated process and is observed in vitro only with strains that have been genetically manipulated to overexpress or disrupt specific regulators, primarily two-component signaling (TCS) regulators. These regulators control biofilm formation by dictating the production of the symbiosis polysaccharide (Syp-PS), the major component of the biofilm matrix. Control occurs both at and below the level of transcription of the syp genes, which are responsible for Syp-PS production. Here, we probed the roles of the two known negative regulators of biofilm formation, BinK and SypE, by generating double mutants. We also mapped and evaluated a point mutation using natural transformation and linkage analysis. We examined traditional biofilm formation phenotypes and established a new assay for evaluating the start of biofilm formation in the form of microscopic aggregates in shaking liquid cultures, in the absence of the known biofilm-inducing signal calcium. We found that wrinkled colony formation is negatively controlled not only by BinK and SypE but also by SypF. SypF is both required for and inhibitory to biofilm formation. Together, these data reveal that these three regulators are sufficient to prevent wild-type V. fischeri from forming biofilms under these conditions.IMPORTANCE Bacterial biofilms promote attachment to a variety of surfaces and protect the constituent bacteria from environmental stresses, including antimicrobials. Understanding the mechanisms by which biofilms form will promote our ability to resolve them when they occur in the context of an infection. In this study, we found that Vibrio fischeri tightly controls biofilm formation using three negative regulators; the presence of a single one of these regulators was sufficient to prevent full biofilm development, while disruption of all three permitted robust biofilm formation. This work increases our understanding of the functions of specific regulators and demonstrates the substantial negative control that one benign microbe exerts over biofilm formation, potentially to ensure that it occurs only under the appropriate conditions.

Project description:Beneficial microbial symbionts are often horizontally acquired by their animal hosts from environmental sources, requiring the symbionts to complete a lifestyle transition from free-living in the environment to association with host tissues. In the model symbiosis between the Hawaiian bobtail squid and its microbial symbiont Vibrio fischeri, one mechanism used to make this transition during host colonization is the formation of biofilm-like aggregates on host mucosa. Extensive work has previously been conducted to isolate the critical factors controlling V. fischeri biofilm formation, yet much remains unknown regarding the full breadth of the biofilm-associated regulon. Here, we probed in vitro models of biofilm formation using transcriptomics, to identify novel regulatory pathways active within biofilms of the V. fischeri type strain ES114. Through comparing the gene-sets which became differentially regulated in multiple biofilm models, we discovered a shared set of 232 genes which demonstrated similar patterns in expression relative to uninduced controls. These genes contained representatives of multiple exopolysaccharide loci, genes involved in flagellar motility, and a diverse collection of other genes. Follow-up analysis suggested that these transcriptomic changes reflected true phenotypic effects, including changes in motility and cyclic-di-GMP production in biofilm-induced backgrounds. Beyond characterizing the shared biofilm response, we additionally profiled the regulatory activity of the sensor kinase RscS. This sensor kinase has previously been characterized to function as a phospho-donor within an established biofilm-inducing phospho-relay, yet our data suggests that RscS moonlights in at least one other phospho-relay that integrates downstream signaling from a homolog of the Vibrio cholerae response regulator VpsR, without a need for its established signaling partners. Overall, this study adds to our understanding of the genes involved in V. fischeri biofilm regulation, while revealing new regulatory pathways branching from previously characterized signaling networks.

Dataset Information

Impact of Salt and Nutrient Content on Biofilm Formation by Vibrio fischeri.

Publications

Impact of Salt and Nutrient Content on Biofilm Formation by Vibrio fischeri.

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