Department of Oral Microbiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima 890-8544, Japan.
Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima 734-8553, Japan.
Microbiology (Reading). 2011 Jun;157(Pt 6):1786-1797. doi: 10.1099/mic.0.044727-0. Epub 2011 Mar 10.
Bacterial cell surface charge is responsible for susceptibility to cationic antimicrobial peptides. Previously, Staphylococcus aureus dlt and mprF were identified as factors conferring a positive charge upon cell surfaces. In this study, we investigated the regulation of cell surface charge during growth. Using a group of S. aureus MW2 mutants, which are gene-inactivated in 15 types of two-component systems (TCSs), we tested dltC and mprF expression and found that two TCSs, aps and agr, were associated with dltC and mprF expression in a growth phase-dependent manner. The first of these, aps, which had already been identified as a sensor of antimicrobial peptides and a positive regulator of dlt and mprF expression, was expressed strongly in the exponential phase, while its expression was significantly suppressed by agr in the stationary phase, resulting in higher expression of dltC and mprF in the exponential phase and lower expression in the stationary phase. Since both types of expression affected the cell surface charge, the susceptibility to antimicrobial peptides and cationic antibiotics was changed during growth. Furthermore, we found that the ability to sense antimicrobial peptides only functioned in the exponential phase. These results suggest that cell surface charge is tightly regulated during growth in S. aureus.
细菌细胞表面电荷决定了其对阳离子抗菌肽的敏感性。先前，金黄色葡萄球菌 dlt 和 mprF 被鉴定为赋予细胞表面正电荷的因素。在这项研究中，我们研究了生长过程中细胞表面电荷的调节。使用一组金黄色葡萄球菌 MW2 突变体，这些突变体在 15 种双组分系统 (TCS) 中基因失活，我们测试了 dltC 和 mprF 的表达，并发现两个 TCS，aps 和 agr，与 dltC 和 mprF 的表达呈生长阶段依赖性相关。其中第一个 aps 已经被鉴定为抗菌肽的传感器和 dlt 和 mprF 表达的正调节剂，在指数生长期表达强烈，而在静止期则被 agr 显著抑制，导致 dltC 和 mprF 在指数生长期表达更高，在静止期表达更低。由于这两种类型的表达都影响了细胞表面电荷，因此在生长过程中抗菌肽和阳离子抗生素的敏感性发生了变化。此外，我们发现感知抗菌肽的能力仅在指数生长期起作用。这些结果表明，金黄色葡萄球菌在生长过程中对细胞表面电荷进行了严格的调节。
