title: Important contribution of the novel locus comEB to extracellular DNA-dependent Staphylococcus lugdunensis biofilm formation.
abstract: The coagulase-negative species Staphylococcus lugdunensis is an emerging cause of serious and potentially life-threatening infections, such as infective endocarditis. The pathogenesis of these infections is characterized by the ability of S. lugdunensis to form biofilms on either biotic or abiotic surfaces. To elucidate the genetic basis of biofilm formation in S. lugdunensis, we performed transposon (Tn917) mutagenesis. One mutant had a significantly reduced biofilm-forming capacity and carried a Tn917 insertion within the competence gene comEB. Site-directed mutagenesis and subsequent complementation with a functional copy of comEB verified the importance of comEB in biofilm formation. In several bacterial species, natural competence stimulates DNA release via lysis-dependent or -independent mechanisms. Extracellular DNA (eDNA) has been demonstrated to be an important structural component of many bacterial biofilms. Therefore, we quantified the eDNA in the biofilms and found diminished eDNA amounts in the comEB mutant biofilm. High-resolution images and three-dimensional data obtained via confocal laser scanning microscopy (CSLM) visualized the impact of the comEB mutation on biofilm integrity. The comEB mutant did not show reduced expression of autolysin genes, decreased autolytic activities, or increased cell viability, suggesting a cell lysis-independent mechanism of DNA release. Furthermore, reduced amounts of eDNA in the comEB mutant biofilms did not result from elevated levels or activity of the S. lugdunensis thermonuclease NucI. In conclusion, we defined here, for the first time, a role for the competence gene comEB in staphylococcal biofilm formation. Our findings indicate that comEB stimulates biofilm formation via a lysis-independent mechanism of DNA release.
authors.affiliation: Institute of Medical Microbiology, University Hospital of Münster, Münster, Germany.
authors.forename: Nithya Babu
authors.initials: NB
authors.lastname: Rajendran
authors.affiliation: Institute of Medical Microbiology, University Hospital of Münster, Münster, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Eikmeier
authors.affiliation: Institute of Medical Microbiology, University Hospital of Münster, Münster, Germany Interdisciplinary Center for Clinical Research (IZKF), University Hospital of Münster, Münster, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Becker
authors.affiliation: Institute of Medical Microbiology, University Hospital of Münster, Münster, Germany.
authors.forename: Muzaffar
authors.initials: M
authors.lastname: Hussain
authors.affiliation: Institute of Medical Microbiology, University Hospital of Münster, Münster, Germany Interdisciplinary Center for Clinical Research (IZKF), University Hospital of Münster, Münster, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Peters
authors.affiliation: Institute of Medical Microbiology, University Hospital of Münster, Münster, Germany Interdisciplinary Center for Clinical Research (IZKF), University Hospital of Münster, Münster, Germany heilmac@uni-muenster.de.
authors.forename: Christine
authors.initials: C
authors.lastname: Heilmann
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D018441:Biofilms / Q000254:growth & development*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D056426:Genetic Loci; D050296:Microbial Viability; D008836:Micrococcal Nuclease / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D015398:Signal Transduction; D057787:Staphylococcus lugdunensis / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D008836:Micrococcal Nuclease