A Clostridium difficile Cell Wall Glycopolymer Locus Influences Bacterial Shape, Polysaccharide Production and Virulence
A Clostridium difficile Cell Wall Glycopolymer Locus Influences Bacterial Shape, Polysaccharide Production and Virulence
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DOI：
10.1371/journal.ppat.1005946
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发表时间：
2016-10-01
期刊：
影响因子：
6.7
通讯作者：
Vedantam, Gayatri
中科院分区：
文献类型：
--
作者：
Chu, Michele;Mallozzi, Michael J. G.;Vedantam, Gayatri
艰难梭菌是一种致泻性病原体，与显著的死亡率和发病率有关。虽然它的糖基化毒素是主要的毒力决定因素，但人们越来越多地认识到非毒素因素在艰难梭菌发病中的重要作用。细胞壁糖共聚物(CWGs)影响多种病原菌的毒力。包括PSII在内的5个艰难梭菌CWG的结构特征已经确定，但它们的生物合成及其在艰难梭菌感染中的意义尚不清楚。我们探索了一个保守的CWG基因座对艰难梭菌细胞表面完整性和毒力的贡献。试图干扰该基因座上的多个基因，包括一个编码CWG出口蛋白mviN的基因，但没有成功，这表明各自的基因产物是必不可少的。然而，反义RNA介导的mviN下调导致了轻微的形态缺陷，抑制了生长，并减少了表面PSII的沉积。另外两个在CWG锚定中可能起作用的基因lcpA和lcpB可能会被插入失活打乱。LcpA(-)和lcpB(-)突变体具有不同的表型，这意味着各自的蛋白质没有多余的作用。突变体lcpB在表面PSII沉积和脱落方面存在缺陷，并表现出重塑的细胞表面，其特征是细长和螺旋的形态，异常定位的细胞隔膜，以及改变的表面锚定蛋白图谱。在艰难梭菌病的仓鼠模型中，lcpA(-)和lcpB(-)菌株也显示出较高的毒力。我们认为艰难梭菌CWG基因座的基因产物是必不可少的，它们指导着关键抗原表面多糖的生产/组装，从而在毒力中具有复杂的作用。
Clostridium difficile is a diarrheagenic pathogen associated with significant mortality and morbidity. While its glucosylating toxins are primary virulence determinants, there is increasing appreciation of important roles for non-toxin factors in C. difficile pathogenesis. Cell wall glycopolymers (CWGs) influence the virulence of various pathogens. Five C. difficile CWGs, including PSII, have been structurally characterized, but their biosynthesis and significance in C. difficile infection is unknown. We explored the contribution of a conserved CWG locus to C. difficile cell-surface integrity and virulence. Attempts at disrupting multiple genes in the locus, including one encoding a predicted CWG exporter mviN, were unsuccessful, suggesting essentiality of the respective gene products. However, antisense RNA-mediated mviN downregulation resulted in slight morphology defects, retarded growth, and decreased surface PSII deposition. Two other genes, lcpA and lcpB, with putative roles in CWG anchoring, could be disrupted by insertional inactivation. lcpA(-) and lcpB(-) mutants had distinct phenotypes, implying non-redundant roles for the respective proteins. The lcpB mutant was defective in surface PSII deposition and shedding, and exhibited a remodeled cell surface characterized by elongated and helical morphology, aberrantly-localized cell septae, and an altered surface-anchored protein profile. Both lcpA(-) and lcpB(-) strains also displayed heightened virulence in a hamster model of C. difficile disease. We propose that gene products of the C. difficile CWG locus are essential, that they direct the production/assembly of key antigenic surface polysaccharides, and thereby have complex roles in virulence.