글루코스 존재하에서 GdpS가 extracellular DNAs 조절을 통해 황색포도알균의 biofilm 형성에 영향을 끼친다

Abstract

The gdpS gene in Staphylococcus aureus contains GGDEF domain, which is implied in diguanyl cyclase activity. Recently, the staphylococcal gdpS gene was proposed to upregulate biofilm formation via icaADBC encoding polysaccharide intercellular adhesin in the presence of NaCl. In this study, deletion of gdpS gene in 8325-4 and seven clinical isolates of S. aureus enhanced the biofilm formation in the presence of glucose in the dose-independent manner. Neither the icaADBC operon nor sigB affected the biofilm formation by the gdpS mutant. In biofilm detachment assays, while either proteinase K or NaIO3 treatment did not affect biofilm integrity, DNase I treatment resulted in greatly reduced biofilm, suggesting that extracellular DNAs (eDNAs) is an important component of the biofilm. The importance of eDNAs in biofilm formation was confirmed by the observation that, in a real time PCR analysis, eDNA level was increased in gdpS mutants compared with that of the parental strain. Inactivation of cidA, holin-like autolysis regulator gene, reversed the biofilm formation of the gdpS mutant of 8325-4. On the contrary, the biofilm formation was still enhanced in the cidA gdpS double mutants of the clinical isolates including YL50, showing that cidA role in biofilm formation depends on the strain background. In addition, autolysis analysis displayed that the gdpS mutant of 8325-4 and the cidA gdpS double mutant of YL50 were the most susceptible to addition of Triton X-100. Interestingly, the enhanced biofilm formation of the cidA gdpS double mutant of CM75 was reversed by disrupting σB, which was not found in the other clinical strains, indicating that the effect of GdpS in 8325-4, which is devoid of σB activity, on biofilm formation via cidA was strain-dependent. Finally, disruption of the atl encoding major autolysin in the gdpS mutants of CM01 and CM09 clinical strains resulted in the lack of the biofilm formation. Collectively, in the presence of glucose, GdpS in S. aureus affects biofilm formation through regulating lysis-associated genes including atl and cidA genes.