Clostridium difficile is an anaerobic and spore-forming bacterium responsible for 15–25% of postantibiotic diarrhea and 95% of pseudomembranous colitis. Peptidoglycan is a crucial element of the bacterial cell wall that is exposed to the host, making it an important target for the innate immune system. The C. difficile peptidoglycan is largely N-deacetylated on its glucosamine (93% of muropeptides) through the activity of enzymes known as N-deacetylases, and this N-deacetylation modulates host–pathogen interactions, such as resistance to the bacteriolytic activity of lysozyme, virulence, and host innate immune responses. C. difficile genome analysis showed that 12 genes potentially encode N-deacetylases; however, which of these N-deacetylases are involved in peptidoglycan N-deacetylation remains unknown. Here, we report the enzymes responsible for peptidoglycan N-deacetylation and their respective regulation. Through peptidoglycan analysis of several mutants, we found that the N-deacetylases PdaV and PgdA act in synergy. Together they are responsible for the high level of peptidoglycan N-deacetylation in C. difficile and the consequent resistance to lysozyme. We also characterized a third enzyme, PgdB, as a glucosamine N-deacetylase. However, its impact on N-deacetylation and lysozyme resistance is limited, and its physiological role remains to be dissected. Finally, given the influence of peptidoglycan N-deacetylation on host defense against pathogens, we investigated the virulence and colonization ability of the mutants. Unlike what has been shown in other pathogenic bacteria, a lack of N-deacetylation in C. difficile is not linked to a decrease in virulence.

中文翻译：

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肽聚糖分析表明，艰难梭菌营养体中的协同脱乙酰酶活性会影响宿主反应。

艰难梭菌是一种厌氧、产孢细菌，导致 15-25% 的抗生素后腹泻和 95% 的伪膜性结肠炎。肽聚糖是暴露于宿主的细菌细胞壁的关键元素，使其成为先天免疫系统的重要目标。艰难梭菌肽聚糖主要通过 N-脱乙酰酶的活性在其葡萄糖胺（93% 的壁肽）上进行 N-脱乙酰化，这种 N-脱乙酰化调节宿主与病原体的相互作用，例如对溶菌酶溶菌活性的抵抗、毒力和宿主先天免疫反应。艰难梭菌基因组分析表明，12 个基因可能编码 N-脱乙酰酶；然而，这些 N-脱乙酰酶中哪些参与肽聚糖 N-脱乙酰化仍然未知。这里，我们报告了负责肽聚糖 N-脱乙酰化的酶及其各自的调节。通过对几个突变体的肽聚糖分析，我们发现N-脱乙酰酶PdaV和PgdA协同作用。它们共同导致艰难梭菌中高水平的肽聚糖 N-脱乙酰化以及随之而来的对溶菌酶的抗性。我们还鉴定了第三种酶 PgdB，它是一种葡萄糖胺 N-脱乙酰酶。然而，它对 N-脱乙酰化和溶菌酶抗性的影响有限，其生理作用仍有待剖析。最后，考虑到肽聚糖 N-脱乙酰化对宿主防御病原体的影响，我们研究了突变体的毒力和定植能力。与其他病原菌中所显示的情况不同，梭菌中缺乏 N-脱乙酰化。