Handke L D, Slater S R, Conlon K M, O'Donnell Sinead T, Olson M E, Bryant K A, Rupp M E, O'Gara J P, Fey P D
Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha 68198-6280, USA.
Can J Microbiol. 2007 Jan;53(1):82-91. doi: 10.1139/w06-108.
The production of polysaccharide intercellular adhesin (PIA) is an essential process in foreign body infections mediated by Staphylococcus epidermidis. Transcriptional regulation of the icaADBC operon, the genes responsible for production of enzymes that synthesize PIA, is multi-factorial and involves at least SarA and sigmaB. Transcriptional and promoter fusion studies revealed that the decreased transcription of the icaADBC operon observed in a S. epidermidis 1457 sigB mutant is not mediated through a direct interaction of sigmaB-RNA polymerase at the icaADBC promoter region but instead through the upregulation of IcaR, a known repressor of icaADBC transcription. Transcriptional analysis of a 1457 sigB-icaR double mutant confirmed that the decreased icaADBC transcript in 1457 sigB is IcaR dependent. Furthermore, primer extension studies suggest that the icaR promoter appears to be sigmaA dependent, suggesting that sigmaB indirectly controls icaR transcription through an unknown pathway. In addition, it was confirmed that the loss of SarA results in the loss of icaADBC transcription and PIA production in S. epidermidis. It was further demonstrated, through the over-production of SarA in 1457 sigB, that the loss of sarP1 promoter activity in 1457 sigB has little or no effect on the loss of PIA production in this mutant. Finally, it was demonstrated that PIA production could be restored in both 1457 sigB and 1457 sarA by complementing these mutants with a full-length icaADBC operon controlled by a cadmium-inducible noncognate promoter. It is concluded that sigmaB and SarA operate independently of each other to regulate PIA production and biofilm development in S. epidermidis.
多糖细胞间黏附素（PIA）的产生是表皮葡萄球菌介导的异物感染中的一个重要过程。icaADBC操纵子负责合成PIA的酶的基因转录调控是多因素的，至少涉及SarA和sigmaB。转录和启动子融合研究表明，在表皮葡萄球菌1457 sigB突变体中观察到的icaADBC操纵子转录减少不是通过sigmaB-RNA聚合酶在icaADBC启动子区域的直接相互作用介导的，而是通过IcaR的上调介导的，IcaR是icaADBC转录的已知阻遏物。对1457 sigB-icaR双突变体的转录分析证实，1457 sigB中icaADBC转录本的减少是IcaR依赖性的。此外，引物延伸研究表明icaR启动子似乎是sigmaA依赖性的，这表明sigmaB通过未知途径间接控制icaR转录。此外，已证实SarA的缺失导致表皮葡萄球菌中icaADBC转录和PIA产生的丧失。通过在1457 sigB中过量表达SarA进一步证明，1457 sigB中sarP1启动子活性的丧失对该突变体中PIA产生的丧失几乎没有影响。最后，通过用由镉诱导的非同源启动子控制的全长icaADBC操纵子补充这些突变体，证明在1457 sigB和1457 sarA中都可以恢复PIA的产生。得出的结论是，sigmaB和SarA相互独立地发挥作用，以调节表皮葡萄球菌中PIA的产生和生物膜的形成。
