DNA damage and reactive nitrogen species are barriers to Vibrio cholerae colonization of the infant mouse intestine.
DNA damage and reactive nitrogen species are barriers to Vibrio cholerae colonization of the infant mouse intestine.
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DOI：
10.1371/journal.ppat.1001295
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发表时间：
2011-02
期刊：
影响因子：
6.7
通讯作者：
Mekalanos JJ
中科院分区：
文献类型：
--
作者：
Davies BW;Bogard RW;Dupes NM;Gerstenfeld TA;Simmons LA;Mekalanos JJ
被摄入的霍乱弧菌通过胃进入宿主的小肠。在这里，我们表明霍乱弧菌需要至少两种类型的DNA修复系统来有效地竞争幼鼠肠道的定植。这些结果表明，霍乱弧菌在小鼠胃肠道中的DNA损伤增加。与此一致，我们表明，与液体培养相比，通过小鼠肠道增加了霍乱弧菌的突变频率。我们的遗传分析确定了已知的和新的防御酶，这些酶是解毒活性氮（但不是活性氧）所需的，也是霍乱弧菌有效定植幼鼠肠道所需的，这表明活性氮是DNA损伤的潜在原因。我们证明了对霍乱弧菌有害的潜在活性氮不是由宿主诱导的一氧化氮合酶（iNOS）活性产生的，而是可能来自胃中酸化的亚硝酸盐。与这一假设一致，我们发现在肠道定植中存在缺陷的DNA修复或活性氮物种防御缺陷的菌株在含亚硝酸盐的酸化培养基中生长下降或突变频率增加。此外，我们证明了中和胃酸可以挽救DNA修复和活性氮物种防御缺陷突变体的定植缺陷，这表明这些突变体有一个共同的防御途径。对细胞内细菌病原体的研究表明，需要保持基因组保真度以促进定植。DNA修复功能的丧失往往导致入侵病原体的衰减和快速清除。然而，对于某些病原体，增加的突变率已被证明有利于促进宿主定植，可能是通过允许病原体迅速适应不利的宿主条件。我们询问非侵入性病原体霍乱弧菌在感染期间是否经历了增加的DNA损伤，如果是这样，增加的损伤如何影响宿主定植以及损伤的来源。我们的研究结果表明，霍乱弧菌在感染婴儿小鼠模型期间经历了增加的DNA损伤，并且修复这种损伤的能力的丧失导致毒性的衰减。我们特别表明，霍乱弧菌需要碱基切除修复和错配修复来实现有效的肠道定植。此外，我们提供的证据表明，DNA损伤的来源来自小鼠肠道中酸化亚硝酸盐形成的活性氮物种（RNS），因此我们在霍乱弧菌和其他几种致病菌中发现了一种新的RNS防御蛋白。
Ingested Vibrio cholerae pass through the stomach and colonize the small intestines of its host. Here, we show that V. cholerae requires at least two types of DNA repair systems to efficiently compete for colonization of the infant mouse intestine. These results show that V. cholerae experiences increased DNA damage in the murine gastrointestinal tract. Agreeing with this, we show that passage through the murine gut increases the mutation frequency of V. cholerae compared to liquid culture passage. Our genetic analysis identifies known and novel defense enzymes required for detoxifying reactive nitrogen species (but not reactive oxygen species) that are also required for V. cholerae to efficiently colonize the infant mouse intestine, pointing to reactive nitrogen species as the potential cause of DNA damage. We demonstrate that potential reactive nitrogen species deleterious for V. cholerae are not generated by host inducible nitric oxide synthase (iNOS) activity and instead may be derived from acidified nitrite in the stomach. Agreeing with this hypothesis, we show that strains deficient in DNA repair or reactive nitrogen species defense that are defective in intestinal colonization have decreased growth or increased mutation frequency in acidified nitrite containing media. Moreover, we demonstrate that neutralizing stomach acid rescues the colonization defect of the DNA repair and reactive nitrogen species defense defective mutants suggesting a common defense pathway for these mutants. Studies on intracellular bacterial pathogens have shown the need for maintaining genomic fidelity to promote colonization. Loss of DNA repair functions often leads to attenuation and rapid clearing of the invading pathogen. However, for some pathogens, an increased mutation rate has been shown to be beneficial for promoting host colonization, presumably by allowing the pathogen to rapidly adapt to adverse host conditions. We asked if the non-invasive pathogen V. cholerae experienced increased DNA damage during infection and if so, how the increased damage influenced host colonization and from where the source of the damage was derived. Our results demonstrate that V. cholerae experiences increased DNA damage during infection in the infant mouse model and that loss of ability to repair this damage results in attenuation of virulence. We specifically show that V. cholerae requires both base excision repair and mismatch repair for efficient intestinal colonization. Furthermore, we present evidence that the source of the DNA damage is derived from reactive nitrogen species (RNS) formed by acidified nitrite in the mouse gut and in doing so we identify a new RNS defense protein found in V. cholerae and several other pathogenic bacteria.
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