SarA is a negative regulator of Staphylococcus epidermidis biofilm formation

Christer Martin, C. Heinze, M. Busch, G. Franke, M. Hentschke, Sara Bayard Dühring, H. Buettner, M. Kotasinska, V. Wischnewski, F. Buck, Søren Molin, Michael Otto, Henning Rohde

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Abstract

Biofilm formation is essential for Staphylococcus epidermidis pathogenicity in implant-associated infections. Nonetheless, large proportions of invasive S. epidermidis isolates fail to show accumulative biofilm growth in vitro. We here tested the hypothesis that this apparent paradox is related to the existence of superimposed regulatory systems suppressing a multi-cellular biofilm life style in vitro. Transposon mutagenesis of clinical significant but biofilm-negative S. epidermidis 1585 was used to isolate a biofilm positive mutant carrying a Tn917 insertion in sarA,chief regulator of staphylococcal virulence. Genetic analysis revealed that inactivation of sarA induced biofilm formation via over-expression of the giant 1 MDa extracellular matrix binding protein (Embp), serving as an intercellular adhesin. In addition to Embp, increased extracellular DNA (eDNA) release significantly contributed to biofilm formation in mutant 1585ΔsarA. Increased eDNA amounts indirectly resulted from up-regulation of metalloprotease SepA, leading to boosted processing of major autolysin AtlE, in turn inducing augmented autolysis and release of chromosomal DNA. Hence, this study identifies sarA as a negative regulator of Embp- and eDNA dependent biofilm formation. Given the importance of SarA as a positive regulator of polysaccharide mediated cell aggregation, the regulator enables S. epidermidis to switch between mechanisms of biofilm formation, ensuring S. epidermidis adaptation to hostile environments.
Original languageEnglish
JournalInternational Journal of Medical Microbiology
Volume302
ISSN1438-4221
Publication statusPublished - 2012
Event64th Annual Meeting of the German-Society-for-Hygiene-and-Microbiology - Congres Center Hamburg (CCH), Hamburg, Germany
Duration: 30 Sep 20123 Oct 2012

Conference

Conference64th Annual Meeting of the German-Society-for-Hygiene-and-Microbiology
LocationCongres Center Hamburg (CCH)
CountryGermany
CityHamburg
Period30/09/201203/10/2012

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