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Enhanced biofilm formation by Escherichia coli LPS mutants defective in Hep biosynthesis.

ABSTRACT: Lipopolysaccharide (LPS) is the major component of the surface of Gram-negative bacteria and its polysaccharide portion is situated at the outermost region. We investigated the relationship between the polysaccharide portion of LPS and biofilm formation using a series of Escherichia coli mutants defective in genes earlier shown to affect the LPS sugar compositions. Biofilm formation by a deep rough LPS mutant, the hldE strain, was strongly enhanced in comparison with the parental strain and other LPS mutants. The hldE strain also showed a phenotype of increased auto-aggregation and stronger cell surface hydrophobicity compared to the wild-type. Similar results were obtained with another deep rough LPS mutant, the waaC strain whose LPS showed same molecular mass as that of the hldE strain. Confocal laser scanning microscopy (CLSM) analysis and biofilm formation assay using DNase I revealed that biofilm formation by the hldE strain was dependent on extracellular DNA. Furthermore, a loss of flagella and an increase in amount of outer membrane vesicles in case of the hldE strain were also observed by transmission electron microscopy and atomic force microscopy, respectively. In addition, we demonstrated that a mutation in the hldE locus, which alters the LPS structure, caused changes in both expression and properties of several surface bacterial factors involved in biofilm formation and virulence. We suggest that the implication of these results should be considered in the context of biofilm formation on abiotic surfaces, which is frequently associated with nosocominal infections such as the catheter-associated infections.

SUBMITTER: Nakao R

PROVIDER: S-EPMC3532297 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Enhanced biofilm formation by Escherichia coli LPS mutants defective in Hep biosynthesis.

Nakao Ryoma R Ramstedt Madeleine M Wai Sun Nyunt SN Uhlin Bernt Eric BE

PloS one 20121228 12

Lipopolysaccharide (LPS) is the major component of the surface of Gram-negative bacteria and its polysaccharide portion is situated at the outermost region. We investigated the relationship between the polysaccharide portion of LPS and biofilm formation using a series of Escherichia coli mutants defective in genes earlier shown to affect the LPS sugar compositions. Biofilm formation by a deep rough LPS mutant, the hldE strain, was strongly enhanced in comparison with the parental strain and othe ...[more]

PMID: 23284671

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Project description:Biofilms in nature typically consist of multiple species, and microbial interactions are likely to have crucial effects on biofilm development, structure, and functions. The best-understood form of communication within bacterial communities involves the production, release, and detection of signal molecules (autoinducers), known as quorum sensing. Although autoinducers mainly promote intraspecies communication, autoinducer 2 (AI-2) is produced and detected by a variety of bacteria, thus principally allowing interspecies communication. Here we show the importance of AI-2-mediated signaling in the formation of mixed biofilms by Enterococcus faecalis and Escherichia coli Our results demonstrate that AI-2 produced by E. faecalis promotes collective behaviors of E. coli at lower cell densities, enhancing autoaggregation of E. coli but also leading to chemotaxis-dependent coaggregation between the two species. Finally, we show that formation of such mixed dual-species biofilms increases the stress resistance of both E. coli and E. faecalis IMPORTANCE The role of interspecies communication in the development of mixed microbial communities is becoming increasingly apparent, but specific examples of such communication remain limited. The universal signal molecule AI-2 is well known to regulate cell-density-dependent phenotypes of many bacterial species but, despite its potential for interspecies communication, the role of AI-2 in the establishment of multispecies communities is not well understood. In this study, we explore AI-2 signaling in a dual-species community containing two bacterial species that naturally cooccur in their mammalian hosts, i.e., Escherichia coli and Enterococcus faecalis We show that active production of AI-2 by E. faecalis allows E. coli to perform collective behaviors at low cell densities. Additionally, AI-2- and chemotaxis-dependent coaggregation with E. faecalis creates nucleation zones for rapid growth of E. coli microcolonies in mixed biofilms and enhances the stress resistance of both species.

Dataset Information

Enhanced biofilm formation by Escherichia coli LPS mutants defective in Hep biosynthesis.

Publications

Enhanced biofilm formation by Escherichia coli LPS mutants defective in Hep biosynthesis.

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