Inactivation of glutamate racemase (MurI) eliminates virulence in Streptococcus mutans
Inactivation of glutamate racemase (MurI) eliminates virulence in Streptococcus mutans
复制标题
谷氨酸消旋酶 (MurI) 失活可消除变形链球菌的毒力
DOI：
10.1016/j.micres.2016.02.003
复制
发表时间：
2016
影响因子：
6.7
通讯作者：
Liang Min
中科院分区：
文献类型：
--
作者：
Zhang Jianying;Liu Jia;Ling Junqi;Tong Zhongchun;Fu Yun;Liang Min
抑制细菌细胞壁合成所需的酶通常是致命的或导致毒力缺陷。谷氨酸消旋酶（MurI）是肽聚糖生物合成的关键酶，已成为治疗的重要靶点;变形链球菌（Streptococcus mutans）是龋病的致病菌之一，具有一系列致龋性毒力因子。然而，关于MurI影响S的发病机制知之甚少。变异体本工作中，S.谷氨酸消旋酶缺陷突变株（S.突变链球菌FW 1718）来研究mur I失活对突变链球菌UA 159致龋毒力的影响。显微镜下观察发现，与野生型相比，突变体的细胞体积增大，细胞链延长，细胞聚集减少，细胞表面超微结构改变。对该突变株的特性分析表明，mur I缺乏会降低S.变异株（P< 0.05）。实时荧光定量聚合酶链反应（qRT-PCR）分析表明，murI基因的缺失使产酸相关基因h的表达量降低了44倍（P< 0.0001）。表面蛋白抗原P基因（spaP）和耐酸相关基因（atpD）的表达下调99%（P< 0.0001）。与生物膜形成相关的基因comE、comD、gtfBandgtfC的表达在突变体中分别是野生型的8、43、85和298倍（P< 0.0001）。综上所述，目前的研究提供了第一个证据表明，MurI缺乏对S。突变毒力特性，使MurI成为控制龋齿的潜在靶点。
Inhibition of enzymes required for bacterial cell wall synthesis is often lethal or leads to virulence defects. Glutamate racemase (MurI), an essential enzyme in peptidoglycan biosynthesis, has been an attractive target for therapeutic interventions.Streptococcus mutans,one of the many etiological factors of dental caries, possesses a series of virulence factors associated with cariogenicity. However, little is known regarding the mechanism by which MurI influences pathogenesis ofS. mutans. In this work, a stable mutant ofS. mutansdeficient in glutamate racemase (S. mutansFW1718) was constructed to investigate the impact ofmurIinactivation on cariogenic virulence inS. mutansUA159. Microscopy revealed that themurImutant exhibited an enlarged cell size, longer cell chains, diminished cell⬜cell aggregation, and altered cell surface ultrastructure compared with the wild-type. Characterization of this mutant revealed thatmurIdeficiency weakened acidogenicity, aciduricity, and biofilm formation ability ofS. mutans(P< 0.05). Real-time quantitative polymerase chain reaction (qRT-PCR) analysis demonstrated that the deletion ofmurIreduced the expression of the acidogenesis-related geneldhby 44-fold (P< 0.0001). The expression levels of the gene coding for surface protein antigen P (spaP) and the acid-tolerance related gene (atpD) were down-regulated by 99% (P< 0.0001). Expression ofcomE,comD,gtfBandgtfC, genes related to biofilm formation, were down-regulated 8-, 43-, 85- and 298-fold in themurImutant compared with the wild-type (P< 0.0001), respectively. Taken together, the current study provides the first evidence that MurI deficiency adversely affectsS. mutansvirulence properties, making MurI a potential target for controlling dental caries.