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Acid-Adaptive Genes of Helicobacter pylori

机译：幽门螺杆菌的酸适应基因

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Helicobacter pylori is the only neutralophile that has been able to colonize the human stomach by using a variety of acid-adaptive mechanisms. One of the adaptive mechanisms is increased buffering due to expression of an acid-activated inner membrane urea channel, UreI, and a neutral pH-optimum intrabacterial urease. To delineate other possible adaptive mechanisms, changes in gene expression in response to acid exposure were examined using genomic microarrays of H. pylori exposed to different levels of external pH (7.4, 6.2, 5.5, and 4.5) for 30 min in the absence and presence of 5 mM urea. Gene expression was correlated with intrabacterial pH measured using 2′,7′-bis-(2-carboxyethyl)-5-carboxyfluorescein and compared to that observed with exposure to 42°C for 30 min. Microarrays containing the 1,534 open reading frames of H. pylori strain 26695 were hybridized with cDNAs from control (pH 7.4; labeled with Cy3) and acidic (labeled with Cy5) conditions. The intrabacterial pH was 8.1 at pH 7.4, fell to 5.3 at pH 4.5, and rose to 6.2 with urea. About 200 genes were up-regulated and ～100 genes were down-regulated at pH 4.5 in the absence of urea, and about half that number changed in the presence of urea. These genes included pH-homeostatic, transcriptional regulatory, motility, cell envelope, and pathogenicity genes. The up-regulation of some pH-homeostatic genes was confirmed by real-time PCR. There was little overlap with the genes induced by temperature stress. These results suggest that H. pylori has evolved multifaceted acid-adaptive mechanisms enabling it to colonize the stomach that may be novel targets for eliminating infection.
机译：幽门螺杆菌（Helicobacter pylori）是唯一能够通过多种酸适应机制在人胃中定殖的嗜中性菌。适应性机制之一是由于酸活化内膜尿素通道UreI和中性pH最佳细菌内尿素酶的表达而增加了缓冲作用。为了描述其他可能的适应性机制，使用 H基因组微阵列检查了响应酸暴露的基因表达变化。在不存在和存在5 mM尿素的情况下，将幽门螺杆菌暴露于不同水平的外部pH（7.4、6.2、5.5和4.5）下30分钟。基因表达与使用2'，7'-双-（2-羧乙基）-5-羧基荧光素测得的细菌内pH相关，并与暴露于42°C 30分钟的观察值进行比较。包含1,534个 H开放阅读框的微阵列。将幽门螺杆菌菌株26695与对照（pH 7.4;用Cy3标记）和酸性（用Cy5标记）条件的cDNA杂交。细菌内pH在pH 7.4时为8.1，在pH 4.5时降至5.3，并用尿素升至6.2。在不存在尿素的情况下，在pH 4.5时，约有200个基因被上调，而向下对〜100个基因进行了下调，而在存在尿素的情况下，约有一半的基因发生了变化。这些基因包括pH稳态，转录调节，运动，细胞包膜和致病性基因。实时PCR证实了某些pH稳态基因的上调。与温度胁迫诱导的基因几乎没有重叠。这些结果表明 H。幽门螺杆菌已经发展了多方面的酸适应机制，使其能够在胃中定植，这可能是消除感染的新靶标。

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