Global regulation by (p)ppGpp and CodY in Streptococcus mutans
Global regulation by (p)ppGpp and CodY in Streptococcus mutans
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DOI：
10.1128/jb.00288-08
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发表时间：
2008-08-01
影响因子：
3.2
通讯作者：
Burne, Robert A.
中科院分区：
文献类型：
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作者：
Lemos, Jose A.;Nascimento, Marcelle A.;Burne, Robert A.
RelA、RelP和RelQ酶负责变形链球菌中alarmone（p）ppGpp的产生。缺乏所有三种合成酶的菌株（Delta relAPQ）在缺乏支链氨基酸（BCAA）亮氨酸或缬氨酸的基本培养基中不能生长，但如果也省略异亮氨酸，则生长良好。在这里，我们研究了在没有亮氨酸和缬氨酸的情况下生长与（p）ppGpp池和CodY的活化之间是否存在相关性。通过使用缺乏（p）ppGpp合成酶的单突变体、双突变体和三突变体的组合，我们证明了在不存在亮氨酸或缬氨酸的情况下生长的能力需要RelP和RelQ产生基础水平的（p）ppGpp。将codY突变引入Delta relAPQ菌株完全恢复了缺乏亮氨酸或缬氨酸的培养基中的生长，揭示了Delta relAPQ的生长缺陷表型与CodY直接相关。通过添加decoyinine降低GTP水平并没有减轻CodY抑制或影响BCAA生物合成相关基因的表达，这表明S。codY不被GTP激活。表型研究结果表明，codY突变体形成生物膜的能力降低，其生长对低pH更敏感，表明CodY在S.变异体微阵列结果揭示了CodY调节子的范围。值得注意的是，在codY突变体中下调的基因上游推定的CodY结合盒的鉴定表明CodY也可能在S.变异人
The RelA, RelP, and RelQ enzymes are responsible for the production of the alarmone (p)ppGpp in Streptococcus mutans. A strain lacking all three synthetases (Delta relAPQ) does not grow in minimal medium lacking the branched-chain amino acids (BCAA) leucine or valine but grows well if isoleucine is also omitted. Here, we investigated whether there was a correlation between growth in the absence of leucine and valine with (p)ppGpp pools and the activation of CodY. By using a combination of single, double, and triple mutants lacking the (p)ppGpp synthetase enzymes, we demonstrated that the ability to grow in the absence of leucine or valine required basal levels of (p) ppGpp production by RelP and RelQ. The introduction of a codY mutation into the Delta relAPQ strain fully restored growth in medium lacking leucine or valine, revealing that the growth-defective phenotype of Delta relAPQ was directly linked to CodY. Lowering GTP levels through the addition of decoyinine did not alleviate CodY repression or affect the expression of genes involved in BCAA biosynthesis, suggesting that S. mutans CodY is not activated by GTP. The results of phenotypic studies revealed that the codY mutant had a reduced capacity to form biofilms and that its growth was more sensitive to low pH, showing a role for CodY in two key virulence properties of S. mutans. Microarray results revealed the extent of the CodY regulon. Notably, the identification of putative CodY-binding boxes upstream of genes that were downregulated in the codY mutant indicates that CodY may also function as a transcriptional activator in S. mutans.