Characterization of a Glutamate Transporter Operon, glnQHMP, in Streptococcus mutans and Its Role in Acid Tolerance
Characterization of a Glutamate Transporter Operon, glnQHMP, in Streptococcus mutans and Its Role in Acid Tolerance
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DOI：
10.1128/jb.01169-09
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发表时间：
2010-02-01
影响因子：
3.2
通讯作者：
Cvitkovitch, Dennis G.
中科院分区：
文献类型：
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作者：
Krastel, Kirsten;Senadheera, Dilani B.;Cvitkovitch, Dennis G.
谷氨酸有助于许多革兰氏阴性和革兰氏阳性细菌的酸耐受性反应（ATR），但其在口腔细菌变形链球菌的ATR中的作用尚不清楚。本研究描述了谷氨酸转运体操纵子的发现和表征，命名为glnQHMP（Smu. 1519呼叫斯穆1522），并研究其在耐酸性中的潜在作用。与野生型UA159菌株相比，glnQHMP的缺失导致放射性标记的谷氨酸转运减少95%。添加谷氨酸代谢UA159细胞导致酸性终产物的产生增加，而glnQHMP突变体产生的乳酸比UA159少，表明谷氨酸代谢和酸产生之间的联系和可能的耐酸性。为了研究这种可能性，我们用谷氨酸盐和在pH 5.5和pH 7.5条件下进行了微阵列分析，其显示谷氨酸盐和弱酸均下调glnQHMP操纵子的表达。我们还测量了UA159及其glnQHMP阴性衍生物在pH 5.5下的生长动力学，发现突变体以比亲本菌株慢得多的速率倍增，但在pH 3.5下的存活率显著优于野生型。综上所述，这些发现支持谷氨酸转运体操纵子glnQHMP参与S.变种人
Glutamate contributes to the acid tolerance response (ATR) of many Gram-negative and Gram-positive bacteria, but its role in the ATR of the oral bacterium Streptococcus mutans is unknown. This study describes the discovery and characterization of a glutamate transporter operon designated glnQHMP (Smu. 1519 to Smu. 1522) and investigates its potential role in acid tolerance. Deletion of glnQHMP resulted in a 95% reduction in transport of radiolabeled glutamate compared to the wild-type UA159 strain. The addition of glutamate to metabolizing UA159 cells resulted in an increased production of acidic end products, whereas the glnQHMP mutant produced less lactic acid than UA159, suggesting a link between glutamate metabolism and acid production and possible acid tolerance. To investigate this possibility, we conducted a microarray analysis with glutamate and under pH 5.5 and pH 7.5 conditions which showed that expression of the glnQHMP operon was downregulated by both glutamate and mild acid. We also measured the growth kinetics of UA159 and its glnQHMP-negative derivative at pH 5.5 and found that the mutant doubled at a much slower rate than the parent strain but survived at pH 3.5 significantly better than the wild type. Taken together, these findings support the involvement of the glutamate transporter operon glnQHMP in the acid tolerance response in S. mutans.