The cidA murein hydrolase regulator contributes to DNA release and biofilm development in Staphylococcus aureus

Rice, K. C. et al. 2007. Proc Natl Acad Sci USA. 104, 8113-8118

Speaker: Kai-yun Lu (呂凱筠)                                       Time: 15:00~16:00, Nov. 7, 2007

Commentator: Dr. Lien-I Hor (何漣漪老師)          Place: Room 601

Abstract:

     Many infections caused by Staphylococcus aureus involve the formation of biofilms, surface-associated communities of microbes encompassed by an extracellular matrix. Previous work by the authors had demonstrated that the cidABC and lrgAB operons of S. aureus regulate cell lysis and antibiotic tolerance. Since their specific functions remain elusive, the authors analyzed the effect of mutation in cidA, the first gene on cid operon, on biofilm development. Their analysis revealed that compared with the wild type S. aureus, the cidA mutant biofilm had a rougher phenotype and less adherence to surface in different models. Propidium iodine staining indicated that the cidA mutant biofilm displayed decreased cell lysis, Quantitative PCR also showed that mutant detected less release of bacterial extracellular genomic DNA (eDNA), a component of the biofilm matrix that has been recently reported to be important for biofilm formation in P. aeruginosa. Exposure of the wild type biofilm to DNase I treatment had a major impact on the structural integrity of the biofilm relative to the cidA mutant strain. Based on these observations, authors suggest that eDNA is an important structural component of the S. aureus biofilm matrix, and that controlled bacterial programmed cell death and lysis is responsible for the release of eDNA.

References:

1.      Whitchurch CB, Tolker-Nielsen T, Ragas PC & Mattick JS. (2002) Science 295, 1487

2.      Allesen-Holm M, Barken KB, Yang L, Klausen M, Webb JS, Kjelleberg S, Molin S, Givskov M & Tolker-Nielsen T. (2006) Mol Microbiol 59, 1114–1128.

3.      Bayles KW. (2007) Nat Rev Microbiol 9, 721-726.