Role of autolysin-mediated DNA release in biofilm formation of Staphylococcus epidermidis

1 Key Laboratory of Medical Molecular Virology of Ministry of Education and Public Health, Institutes of Biomedical Sciences and Medical Microbiology, Shanghai Medical School of Fudan University Box 228, Yi Xue Yuan Road 138#, Shanghai 200032, P. R. China 2 BioCentrum-DTU, Building 301, Technical University of Denmark, DK-2800 Lyngby, Denmark Correspondence Soeren Molin sm{at}biocentrum.dtu.dk Staphylococcus epidermidis has become a serious nosocomial pathogen frequently causing infections associated with implanted foreign materials. Biofilm formation is considered a major factor determining S. epidermidis pathogenicity in such device-associated infections. Here, evidence is presented that extracellular DNA is important for the initial phase of biofilm development by S. epidermidis on polystyrene or glass surfaces under static or hydrodynamic conditions. Comparative PCR amplification from S. epidermidis chromosomal and extracellular DNA indicated that the extracellular DNA is similar to chromosomal DNA. Experiments involving the S. epidermidis wild-type and an isogenic atlE mutant indicated that most of the extracellular DNA in S. epidermidis cultures and biofilms is generated through activity of the autolysin AtlE. The presented results suggest that extracellular DNA is generated in S. epidermidis populations through AtlE-mediated lysis of a subpopulation of the bacteria, and that the extracellular DNA promotes biofilm formation of the remaining population. Abbreviations: CLSM, confocal laser scanning microscopy; DDAO, 7-hydroxy-9 H -(1,3-dichloro-9,9-dimethylacridin-2-one); EPS, extracellular polymeric substance; PI, propidium iodide These authors contributed equally to this work.