...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of bacteriology >Defects in d-Alanyl-Lipoteichoic Acid Synthesis in Streptococcus mutans Results in Acid Sensitivity
【24h】

Defects in d-Alanyl-Lipoteichoic Acid Synthesis in Streptococcus mutans Results in Acid Sensitivity

机译：变形链球菌中d-丙氨酰-脂磷壁酸合成的缺陷导致酸敏感性

获取原文
   

获取外文期刊封面封底 >>

       
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

In the cariogenic organism, Streptococcus mutans, low pH induces an acid tolerance response (ATR). To identify acid-regulated proteins comprising the ATR, transposon mutagenesis with the thermosensitive plasmid pGh9:ISS1 was used to produce clones that were able to grow at neutral pH, but not in medium at pH 5.0. Sequence analysis of one mutant (IS1A) indicated that transposition had created a 6.3-kb deletion, one end of which was indltB of the dlt operon encoding four proteins (DltA-DltD) involved in the synthesis ofd-alanyl-lipoteichoic acid. Inactivation of thedltC gene, encoding the d-alanyl carrier protein (Dcp), resulted in the generation of the acid-sensitive mutant, BH97LC. Compared to the wild-type strain, LT11, the mutant exhibited a threefold-longer doubling time and a 33% lower growth yield. In addition, it was unable to initiate growth below pH 6.5 and unadapted cells were unable to survive a 3-h exposure in medium buffered at pH 3.5, while a pH of 3.0 was required to kill the wild type in the same time period. Also, induction of the ATR in BH97LC, as measured by the number of survivors at a pH killing unadapted cells, was 3 to 4 orders of magnitude lower than that exhibited by the wild type. While the LTA of both strains contained a similar average number of glycerolphosphate residues, permeabilized cells of BH97LC did not incorporated-[14C]alanine into this amphiphile. This defect was correlated with the deficiency of Dcp. Chemical analysis of the LTA purified from the mutant confirmed the absence ofd-alanine-esters. Electron micrographs showed that BH97LC is characterized by unequal polar caps and is devoid of a fibrous extracellular matrix present on the surface of the wild-type cells. Proton permeability assays revealed that the mutant was more permeable to protons than the wild type. This observation suggests a mechanism for the loss of the characteristic acid tolerance response in S. mutans.
机译：在致龋菌变形链球菌中，低pH值会诱导耐酸反应（ATR）。为了鉴定包含ATR的酸调节蛋白，使用具有热敏质粒pGh9：IS S1 的转座子诱变产生了能够在中性pH下生长的克隆，但不能在pH 5.0的培养基中生长。对一个突变体（IS1A）进行的序列分析表明，转座产生了6.3kb的缺失，其一端位于编码4种蛋白质（DltA- DltD）参与了d-丙氨酰-脂酸的合成。编码d-丙氨酰载体蛋白（Dcp）的 dltC 基因失活导致了酸敏感突变体BH97LC的产生。与野生型菌株LT11相比，该突变体表现出更长的三倍加倍时间和33％的低增长产量。另外，它不能在pH 6.5以下开始生长，并且未适应的细胞在pH 3.5缓冲的培养基中不能存活3小时，而在同一时间杀死野生型则需要pH 3.0。同样，BH97LC中ATR的诱导（通过在pH值下杀死未适应细胞的存活者的数量来衡量）比野生型低3至4个数量级。尽管两个菌株的LTA均含有相似的甘油磷酸酯残基平均数，但BH97LC的透化细胞未将-[ 14 C]丙氨酸掺入该两亲物中。该缺陷与Dcp的缺乏有关。从突变体纯化的LTA的化学分析证实不存在d-丙氨酸酯。电子显微照片显示，BH97LC的特征是不相等的极性帽，并且在野生型细胞表面没有纤维状细胞外基质。质子渗透性测定表明，该突变体比野生型对质子的渗透性更高。该观察结果提示了在 S中丧失特征酸耐受性反应的机制。变形。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号