The role of Staphylococcus aureus surface protein SasG in adherence and biofilm formation
The role of Staphylococcus aureus surface protein SasG in adherence and biofilm formation
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DOI：
10.1099/mic.0.2007/006676-0
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发表时间：
2007-08-01
期刊：
影响因子：
2.8
通讯作者：
Foster, Timothy J.
中科院分区：
文献类型：
--
作者：
Corrigan, Rebecca M.;Rigby, David;Foster, Timothy J.
金黄色葡萄球菌定植于前鼻孔的湿润鳞状上皮。可能起作用的粘附素之一是条下的（S）。 (a)bar下的ureus(s)下的bar下的表面蛋白(G)(SasG)，其与金黄色葡萄球菌的蛋白质Pls((p)下的bar下的lasmin(s)下的bar敏感)和表皮葡萄球菌的Aap((a)下的bar累积相关蛋白)具有序列相似性。蛋白质免疫印迹无法检测到金黄色葡萄球菌实验室菌株的 SasG 表达。为了能够研究 SasG，将该基因克隆到两个表达载体（IPTG 诱导型 pMUTIN4 和四环素诱导型 pALC2073）中，并引入金黄色葡萄球菌中。 SasG 的表达掩盖了表达蛋白 A (Spa)、聚集因子 B (ClfB) 和纤连蛋白结合蛋白 A 和 B（FnBPA 和 FnBPB）的指数生长金黄色葡萄球菌细胞分别与 IgG、细胞角蛋白 10 和纤连蛋白结合的能力。 SasG 还掩盖了 CIfB 和 FnBP 介导的与纤维蛋白原的结合。蛋白质免疫印迹显示，在诱导 SasG 后，被阻断的粘附素的表达没有减少。具有八个、六个或五个 B 重复的 SasG 大小变体掩盖了与配体的结合，而具有四个、两个或一个重复的变体则没有效果。表达 SasG 的菌株在细胞壁上形成不同密度的周毛原纤维（长 53.47 +/- 2.51 nm），并通过抗 SasG 抗体的免疫金负染色进行标记。表达 SasG 的金黄色葡萄球菌菌株也形成独立于多糖细胞间粘附素 (PIA) 的生物膜。具有八个、六个和五个重复的 SasGi 变体形成了生物膜，而具有四个、两个或一个重复的变体则没有。结论是，SasG 的纤维性质解释了它能够掩盖识别粘附基质分子 (MSCRAMM) 的金黄色葡萄球菌微生物表面成分与其配体的结合，并促进生物膜的形成。此外，SasG 对脱落的鼻上皮细胞的强烈粘附可能补偿了其对金黄色葡萄球菌 ClfB 与细胞角蛋白 10 结合的阻断，这对于缺乏 SasG 的细胞与鳞屑的粘附很重要。一些临床分离株表达 SasG 的水平与 SH 1000 sasG::pMUTIN4 相似，表明实验室菌株 SH 1000 中描述的特性可能与体内相关。
Staphylococcus aureus colonizes the moist squamous epithelium of the anterior nares. One of the adhesins likely to be responsible is the (S) under bar. (a) under bar ureus (s) under bar urface protein (G) under bar (SasG), which has sequence similarity with the proteins Pls ((p) under bar lasmin (s) under bar ensitive) of S. aureus and Aap ((a) under bar ccumulation associated protein) of Staphylococcus epidermidis. Expression of SasG by a laboratory strain of S. aureus could not be detected by Western immunoblotting. To enable investigation of SasG, the gene was cloned into two expression vectors, the IPTG-inducible pMUTIN4 and the tetracycline-inducible pALC2073, and introduced into S. aureus. Expression of SasG masked the ability of exponentially grown S. aureus cells expressing protein A (Spa), clumping factor B (ClfB) and the fibronectin binding proteins A and B (FnBPA and FnBPB) to bind to IgG, cytokeratin 10 and fibronectin, respectively. SasG also masked binding to fibrinogen mediated by both CIfB and the FnBPs. Western immunoblotting showed no reduction in expression of the blocked adhesins following induction of SasG. SasG size variants with eight, six or five B repeats masked binding to the ligands, whereas variants with four, two or one repeats had no effect. SasG-expressing strains formed peritrichous fibrils (53.47 +/- 2.51 nm long) of varying density on the cell wall, which were labelled by immunogold negative staining with anti-SasG antibodies. SasG-expressing strains of S. aureus also formed biofilm independently of the polysaccharide intercellular adhesin (PIA). SasGi variants with eight, six and five repeats formed biofilm, whereas variants with four, two or one repeats did not. It was concluded that the fibrillar nature of SasG explains its ability to mask binding of S. aureus microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) to their ligands and to promote formation of biofilm. In addition, the strong adhesion of SasG to desquamated nasal epithelial cells likely compensates for its blocking of the binding of S. aureus ClfB to cytokeratin 10, which is important in adhesion to squames by cells lacking SasG. Several clinical isolates expressed SasG at levels similar to those of SH 1000 sasG: : pMUTIN4, indicating that the properties described in the laboratory strain SH 1000 may be relevant in vivo.