Genetic Diversity as Consequence of a Microaerobic and Neutrophilic Lifestyle
Genetic Diversity as Consequence of a Microaerobic and Neutrophilic Lifestyle
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DOI：
10.1371/journal.ppat.1005626
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发表时间：
2016-05-01
期刊：
影响因子：
6.7
通讯作者：
Stingl, Kerstin
中科院分区：
文献类型：
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作者：
Krueger, Nora-Johanna;Knuever, Marie-Theres;Stingl, Kerstin
作为一种中性粒细胞，幽门螺杆菌在极端酸性条件下生长不足。胃病原体配备了酸生存套件，通过 pH 门控尿素通道（在 pH 6.5 以下打开）调节尿素酶活性。克服酸应激后，细菌的增殖部位位于pH值接近中性的胃粘膜。该病原体表现出特殊的遗传变异性，这主要是由于其自然转化的能力，称为能力。通过单细胞分析，我们在此表明，幽门螺杆菌的能力受到高度调控。当 pH 值低于 6.5 时，DNA 摄取复合物活性可逆地关闭。 pH 值高于 6.5 打开了一个能力窗口，其中 pH 值升高和氧化应激的结合触发了能力的发展。相比之下，添加亚致死浓度的 DNA 损伤剂环丙沙星或丝裂霉素 C 在我们的条件下不会引发能力发展。在相当的条件下，缺乏超氧化物歧化酶（sodB）的氧敏感突变体比野生型表现出更高的细胞活性部分。此外，sodB突变体在肉汤中的生长依赖于腺嘌呤，并且在没有腺嘌呤的情况下转变成不可培养的球状形式，表明腺嘌呤具有自由基猝灭能力。对感受态野生型细胞中位于周质的 DNA 进行定量显示，在导入后 10 分钟内，每个细胞的平均导入 DNA 量约为 350 kb，单个细胞中的最大染色体当量 (1.6 Mb)，远远超过之前在其他革兰氏阴性细菌中检测到的量。我们得出的结论是，病原体的高遗传多样性是其巨大的 DNA 摄取能力的结果，一旦慢性宿主定植部位的中性 pH 值允许能力发展，内在和外在氧化应激就会引发这种能力。
As a neutrophilic bacterium, Helicobacter pylori is growth deficient under extreme acidic conditions. The gastric pathogen is equipped with an acid survival kit, regulating urease activity by a pH-gated urea channel, opening below pH 6.5. After overcoming acid stress, the bacterium's multiplication site is situated at the gastric mucosa with near neutral pH. The pathogen exhibits exceptional genetic variability, mainly due to its capability of natural transformation, termed competence. Using single cell analysis, we show here that competence is highly regulated in H. pylori. DNA uptake complex activity was reversibly shut down below pH 6.5. pH values above 6.5 opened a competence window, in which competence development was triggered by the combination of pH increase and oxidative stress. In contrast, addition of sublethal concentrations of the DNA-damaging agents ciprofloxacin or mitomycin C did not trigger competence development under our conditions. An oxygen-sensitive mutant lacking superoxide dismutase (sodB) displayed a higher competent fraction of cells than the wild type under comparable conditions. In addition, the sodB mutant was dependent on adenine for growth in broth and turned into non-cultivable coccoid forms in its absence, indicating that adenine had radical quenching capacity. Quantification of periplasmically located DNA in competent wild type cells revealed outstanding median imported DNA amounts of around 350 kb per cell within 10 min of import, with maximally a chromosomal equivalent (1.6 Mb) in individual cells, far exceeding previous amounts detected in other Gram-negative bacteria. We conclude that the pathogen's high genetic diversity is a consequence of its enormous DNA uptake capacity, triggered by intrinsic and extrinsic oxidative stress once a neutral pH at the site of chronic host colonization allows competence development.