The Group B Streptococcus NADH oxidase Nox‐2 is involved in fatty acid biosynthesis during aerobic growth and contributes to virulence
The Group B Streptococcus NADH oxidase Nox‐2 is involved in fatty acid biosynthesis during aerobic growth and contributes to virulence
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DOI：
10.1111/j.1365-2958.2006.05406.x
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发表时间：
2006-11
影响因子：
3.6
通讯作者：
Yuji Yamamoto;V. Pargade;G. Lamberet;P. Gaudu;Fabrice Thomas;J. Texereau;A. Gruss;P. Trieu-Cuot;C. Poyart
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文献类型：
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作者：
Yuji Yamamoto;V. Pargade;G. Lamberet;P. Gaudu;Fabrice Thomas;J. Texereau;A. Gruss;P. Trieu-Cuot;C. Poyart
许多链球菌科产生H2O-形成NADH氧化酶，Nox-2，其通常与有氧生存有关。我们研究了Nox-2在新生儿感染的主要病原体B族链球菌（GBS）中的作用。虽然nox2失活导致需氧生长停滞，但通过向培养物中添加抗氧化剂没有看到改善，这表明这种缺陷不是由于有毒氧物质的积累。使用几种方法，我们表明，观察到的nox 2突变体不能有氧生长主要是由于脂肪酸（FA）生物合成的潜在缺陷：（i）通过向培养基中加入油酸来充分和快速地补充NOX 2需氧生长缺陷，和（ii）在野生型（WT）和nox 2 GBS膜中这种不饱和FA的直接同化被证明并与突变体生长拯救相关。我们提出nox2突变体中NAD+的耗尽导致乙酰辅酶A的产生减少，这干扰了FA的生物合成，从而阻止了有氧生长。当外源血红素和甲基萘醌激活GBS呼吸代谢时，nox2需氧生长缺陷也得到了补充。因此，由功能性呼吸链产生的膜NADH氧化酶活性补偿细胞质NADH氧化酶缺乏。如在肺、腹膜内和静脉内小鼠感染模型中所评估的，nox2突变体的毒力被减弱。由于nox2缺陷似乎只影响GBS的有氧生长，其降低的毒力支持有氧条件和NADH氧化酶活性与GBS感染过程相关的建议。
Numerous Streptococcaceae produce an H2O‐forming NADH oxidase, Nox‐2, which has been generally implicated in aerobic survival. We examined the roles of Nox‐2 in Group B Streptococcus (GBS), a leading agent of neonatal infections. While nox2 inactivation caused an aerobic growth arrest, no improvement was seen by addition of antioxidants to cultures, suggesting that this defect was not due to accumulation of toxic oxygen species. Using several approaches, we show that the observed inability of the nox2 mutant to grow aerobically is mainly due to an underlying defect in fatty acid (FA) biosynthesis: (i) the nox2 aerobic growth defect is fully and rapidly complemented by adding oleic acid to culture medium, and (ii) direct assimilation of this unsaturated FA in both wild type (WT) and nox2 GBS membranes is demonstrated and correlated with mutant growth rescue. We propose that NAD+ depletion in the nox2 mutant results in reduced acetyl‐CoA production, which perturbs FA biosynthesis and hence blocks growth in aerobiosis. The nox2 aerobic growth defect was also complemented when GBS respiration metabolism was activated by exogenous haem and menaquinone. The membrane NADH oxidase activity generated by the functional respiratory chain thus compensates the cytoplasmic NADH oxidase deficiency. The nox2 mutant was attenuated for virulence, as assessed in lung, intraperitoneal and intravenous murine infection models. As the nox2 defect seems only to affect aerobic growth of GBS, its reduced virulence supports the suggestion that aerobic conditions and NADH oxidase activities are relevant to the GBS infection process.