New insights into the pneumococcal fratricide:: relationship to clumping and identification of a novel immunity factor
New insights into the pneumococcal fratricide:: relationship to clumping and identification of a novel immunity factor
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DOI：
10.1111/j.1365-2958.2005.05021.x
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发表时间：
2006-02-01
影响因子：
3.6
通讯作者：
Claverys, JP
中科院分区：
文献类型：
--
作者：
Håvarstein, LS;Martin, B;Claverys, JP
1971年，Tomasz和Zanati发现，当离心造粒并在0.01盐酸中短暂旋转重悬时，活性肺炎球菌有形成聚集体的倾向。有趣的是，以相同方式处理的非能态细胞的平行培养未观察到结块。我们着手阐明这一惊人现象背后的机制，并能够证明它取决于细胞外DNA，这可能是由所谓的能力诱导的细胞裂解释放的。几年前首次描述的能力诱导细胞裂解似乎依赖于几种鼠蛋白水解酶的协同作用。我们的研究结果证实并扩展了之前的发现，表明在lytA-lytC双突变体中，能力诱导的聚集被消除，并且绝对需要CbpD及其n端CHAP酰胺酶结构域。此外，我们发现了一种新的能力刺激肽（CSP）诱导的免疫蛋白，由早期能力基因comM （spr1762）编码，可以保护能力肺炎球菌免受自身溶酶的侵害。鼠蛋白水解酶和免疫蛋白共同构成了一个由csp控制的机制，允许有能力的肺炎球菌通过杀死共享同一生态位的非有能力的肺炎球菌来实施自相残杀。通过这种掠夺行为，肺炎球菌可以获得转化DNA和营养物质，促进毒力因子的释放，同时摆脱竞争对手。
In 1971, Tomasz and Zanati discovered that competent pneumococci have a tendency to form aggregates when pelleted by centrifugation and resuspended in 0.01 N HCl by brief vortexing. Interestingly, no clumping was observed with parallel cultures of non-competent cells treated in the same way. We set out to elucidate the mechanism behind this striking phenomenon, and were able to show that it depends on extracellular DNA that is presumably released by so-called competence-induced cell lysis. Competence-induced cell lysis, which was first described a few years ago, seems to rely on the concerted action of several murein hydrolases. Our results confirmed and extended previous findings by showing that competence-induced aggregation is abolished in a lytA-lytC double mutant, and absolutely requires CbpD and its N-terminal CHAP amidase domain. Furthermore, we discovered a novel competence stimulating peptide (CSP)-induced immunity protein, encoded by the early competence gene comM (spr1762), which protects competent pneumococci against their own lysins. Together, the murein hydrolases and the immunity protein constitutes a CSP-controlled mechanism that allows competent pneumococci to commit fratricide by killing non-competent pneumococci sharing the same ecological niche. Through such predatory behaviour, pneumococci can get access to transforming DNA and nutrients, promote the release of virulence factors, and at the same time get rid of competitors.