Helicobacter pylori peptidoglycan modifications confer lysozyme resistance and contribute to survival in the host.
Helicobacter pylori peptidoglycan modifications confer lysozyme resistance and contribute to survival in the host.
复制标题
幽门螺杆菌肽聚糖修饰赋予溶菌酶抗性并有助于在宿主中生存。
DOI：
10.1128/mbio.00409-12
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发表时间：
2012
期刊：
影响因子：
6.4
通讯作者：
Maier,RobertJ
中科院分区：
文献类型：
--
作者：
Wang,Ge;Lo,LejaF;Forsberg,LennartS;Maier,RobertJ
主要宿主溶菌酶裂解细菌肽聚糖（PG），这种酶在粘膜分泌物中含量丰富。革兰氏阴性菌的溶解酶敏感性和它们用来阻碍溶解酶活性的机制研究得很少。我们以前的特点是幽门螺杆菌PG修饰酶，N-脱乙酰酶（PgdA）参与溶菌酶耐药性。在这项研究中，另一个PG修饰酶，一个假定的PG O-乙酰转移酶（PatA），被确定。纯化PG的质谱分析表明，apatA菌株含有大大减少的乙酰化胞肽，表明PatA在H. pylori PG O-乙酰化。PG修饰突变株（pgdA、patA、orpgdA patA）比亲本对溶菌酶杀伤更敏感，但该测定需要高的溶菌酶水平（高达50 mg/ml）。然而，添加宿主乳铁蛋白赋予溶菌酶对H.幽门螺杆菌，在两种宿主组分的生理相关浓度（3 mg/ml乳铁蛋白加0.3mg/ml溶菌酶）下。pgdA patAdouble突变株对溶菌酶/乳铁蛋白杀伤的敏感性远高于亲本。从apgdA patA突变体纯化的肽聚糖对溶菌酶的敏感性是来自亲本菌株的PG的5倍，而来自两个单突变体的PG显示出中等的敏感性。对全细胞和纯化的PG的敏感性测定表明，由PgdA和PatA介导的修饰具有协同效应，赋予溶菌酶耐受性。在小鼠感染模型中，在接种后3周观察到双突变体的显著定殖缺陷。结果表明，PG修饰影响革兰氏阴性病原体的存活。重要病原菌逃避宿主抗菌酶的多种机制，其中包括抵抗溶解酶丰富的主机。对肽聚糖（PG，溶菌酶的作用位点）的酶促修饰是革兰氏阳性菌用于保护免受宿主溶菌酶攻击的已知机制。然而，革兰氏阴性菌含有一层薄薄的PG和一个可抵抗裂解的外膜渗透屏障，因此为了对抗裂解而对细胞壁结构进行的分子修饰在很大程度上尚未研究。在这里，我们表明，两个幽门螺杆菌PG修饰酶（PgdA和PatA）赋予一个明确的保护优势，革兰氏阴性菌。它们保护细菌免于裂解酶降解，尽管是通过不同的PG修饰活性。许多病原体是革兰氏阴性的，因此预计有些病原体具有类似的细胞壁修饰策略。了解这些策略可能有助于对抗病原体的生长。
The prominent host muramidase lysozyme cleaves bacterial peptidoglycan (PG), and the enzyme is abundant in mucosal secretions. The lytic enzyme susceptibility of Gram-negative bacteria and mechanisms they use to thwart lytic enzyme activity are poorly studied. We previously characterized a Helicobacter pylori PG modification enzyme, an N-deacetylase (PgdA) involved in lysozyme resistance. In this study, another PG modification enzyme, a putative PG O-acetyltransferase (PatA), was identified. Mass spectral analysis of the purified PG demonstrated that apatAstrain contained a greatly reduced amount of acetylated muropeptides, indicating a role for PatA in H. pylori PG O-acetylation. The PG modification mutant strains (pgdA,patA, orpgdA patA) were more susceptible to lysozyme killing than the parent, but this assay required high lysozyme levels (up to 50 mg/ml). However, addition of host lactoferrin conferred lysozyme sensitivity to H. pylori, at physiologically relevant concentrations of both host components (3 mg/ml lactoferrin plus 0.3 mg/ml lysozyme). ThepgdA patAdouble mutant strain was far more susceptible to lysozyme/lactoferrin killing than the parent. Peptidoglycan purified from apgdA patAmutant was five times more sensitive to lysozyme than PG from the parent strain, while PG from both single mutants displayed intermediate sensitivity. Both sensitivity assays for whole cells and for purified PGs indicated that the modifications mediated by PgdA and PatA have a synergistic effect, conferring lysozyme tolerance. In a mouse infection model, significant colonization deficiency was observed for the double mutant at 3 weeks postinoculation. The results show that PG modifications affect the survival of a Gram-negative pathogen.IMPORTANCEPathogenic bacteria evade host antibacterial enzymes by a variety of mechanisms, which include resisting lytic enzymes abundant in the host. Enzymatic modifications to peptidoglycan (PG, the site of action of lysozyme) are a known mechanism used by Gram-positive bacteria to protect against host lysozyme attack. However, Gram-negative bacteria contain a thin layer of PG and a recalcitrant outer membrane permeability barrier to resist lysis, so molecular modifications to cell wall structure in order to combat lysis remain largely unstudied. Here we show that two Helicobacter pylori PG modification enzymes (PgdA and PatA) confer a clear protective advantage to a Gram-negative bacterium. They protect the bacterium from lytic enzyme degradation, albeit via different PG modification activities. Many pathogens are Gram negative, so some would be expected to have a similar cell wall-modifying strategy. Understanding such strategies may be useful for combating pathogen growth.