Wu Yang, Liu Jingran, Jiang Juan, Hu Jian, Xu Tao, Wang Jiaxue, Qu Di
Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China.
Key Laboratory of Medical Molecular Virology of Ministries of Education and Health, Institute of Medical Microbiology and Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, PR China.
Microb Pathog. 2014 Nov;76:89-98. doi: 10.1016/j.micpath.2014.09.013. Epub 2014 Sep 26.
The ica operon and aap gene are important factors for Staphylococcus epidermidis biofilm formation. However, we found 15 out of 101 S. epidermidis strains isolated from patients had both the ica operon and the aap gene in the genome but could not form biofilms (ica(+)aap(+)/BF(-) isolates). Compared with standard strain RP62A, the 15 ica(+)aap(+)/BF(-) isolates had similar growth curves and initial attachment abilities, but had much lower apparent transcription levels of the icaA gene and significantly less production of polysaccharide intercellular adhesion (PIA). Furthermore, the expression of accumulation-associated protein in ica(+)aap(+)/BF(-) isolates was much weaker than in RP62A. The mRNA levels of icaADBC transcription-related regulatory genes, including icaR, sarA, rsbU, srrA, arlRS and luxS, were measured in the 15 ica(+)aap(+)/BF(-) clinical isolates. The mRNA levels of arlR and rsbU in all of the ica(+)aap(+)/BF(-) isolates were lower than in RP62A at 4 h. At 10 h, 14/15 of the isolates showed lower mRNA levels of arlR and rsbU than shown by RP62A. However, expression of sarA, luxS, srrA and icaR varied in different ica(+)aap(+)/BF(-) isolates. To further investigate the role of arlRS in biofilm formation, we analyzed icaA, sarA and rsbU transcription, PIA synthesis, Aap expression and biofilm formation in an arlRS deletion mutant of S. epidermidis strain 1457 and all were much less than in the wild type strain. This is consistent with the hypothesis that ArlRS may play an important role in regulating biofilm formation by the ica(+)aap(+)/BF(-)S. epidermidis clinical isolates and operate via both ica-dependent and Aap-dependent pathways.
ica操纵子和aap基因是表皮葡萄球菌生物膜形成的重要因素。然而，我们发现从患者中分离出的101株表皮葡萄球菌菌株中有15株在基因组中同时具有ica操纵子和aap基因，但无法形成生物膜（ica(+)aap(+)/BF(-)分离株）。与标准菌株RP62A相比，这15株ica(+)aap(+)/BF(-)分离株具有相似的生长曲线和初始附着能力，但icaA基因的表观转录水平低得多，胞间多糖黏附素（PIA）的产生也显著减少。此外，ica(+)aap(+)/BF(-)分离株中积累相关蛋白的表达比RP62A弱得多。在这15株ica(+)aap(+)/BF(-)临床分离株中检测了icaADBC转录相关调控基因（包括icaR、sarA、rsbU、srrA、arlRS和luxS）的mRNA水平。在4小时时，所有ica(+)aap(+)/BF(-)分离株中arlR和rsbU的mRNA水平均低于RP62A。在10小时时，15株分离株中有14株显示arlR和rsbU的mRNA水平低于RP62A。然而，sarA、luxS、srrA和icaR的表达在不同的ica(+)aap(+)/BF(-)分离株中有所不同。为了进一步研究arlRS在生物膜形成中的作用，我们分析了表皮葡萄球菌菌株1457的arlRS缺失突变体中的icaA、sarA和rsbU转录、PIA合成、Aap表达和生物膜形成，所有这些均远低于野生型菌株。这与以下假设一致，即ArlRS可能在调节ica(+)aap(+)/BF(-)表皮葡萄球菌临床分离株的生物膜形成中起重要作用，并通过ica依赖性和Aap依赖性途径发挥作用。
