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首页> 外文期刊>Infection and immunity >An Escherichia coli MG1655 Lipopolysaccharide Deep-Rough Core Mutant Grows and Survives in Mouse Cecal Mucus but Fails To Colonize the Mouse Large Intestine
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An Escherichia coli MG1655 Lipopolysaccharide Deep-Rough Core Mutant Grows and Survives in Mouse Cecal Mucus but Fails To Colonize the Mouse Large Intestine

机译：大肠杆菌MG1655脂多糖深粗糙核心突变体在小鼠盲肠粘液中生长和存活，但未能在小鼠大肠上定殖

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The ability of E. coli strains to colonize the mouse large intestine has been correlated with their ability to grow in cecal and colonic mucus. In the present study, an E. coli MG1655 strain was mutagenized with a mini-Tn5 Km (kanamycin) transposon, and mutants were tested for the ability to grow on agar plates with mouse cecal mucus as the sole source of carbon and nitrogen. One mutant, designated MD42 (for mucus defective), grew poorly on cecal-mucus agar plates but grew well on Luria agar plates and on glucose minimal-agar plates. Sequencing revealed that the insertion in MD42 was in the waaQ gene, which is involved in lipopolysaccharide (LPS) core biosynthesis. Like “deep-rough” E. coli mutants, MD42 was hypersensitive to sodium dodecyl sulfate (SDS), bile salts, and the hydrophobic antibiotic novobiocin. Furthermore, its LPS core oligosaccharide was truncated, like that of a deep-rough mutant. MD42 initially grew in the large intestines of streptomycin-treated mice but then failed to colonize (<102 CFU per g of feces), whereas its parent colonized at levels between 107 and 108 CFU per g of feces. When mouse cecal mucosal sections were hybridized with an E. coli-specific rRNA probe, MD42 was observed in cecal mucus as clumps 24 h postfeeding, whereas its parent was present almost exclusively as single cells, suggesting that clumping may play a role in preventing MD42 colonization. Surprisingly, MD42 grew nearly as well as its parent during growth in undiluted, highly viscous cecal mucus isolated directly from the mouse cecum and, like its parent, survived well after reaching stationary phase, suggesting that there are no antimicrobials in mucus that prevent MD42 colonization. After mini-mariner transposon mutagenesis, an SDS-resistant suppressor mutant of MD42 was isolated. The mini-mariner insertion was shown to be in the bipA gene, a known regulator of E. coli surface components. When grown in Luria broth, the LPS core of the suppressor mutant remained truncated; however, the LPS core was not truncated when the suppressor mutant was grown in the presence of SDS. Moreover, when the suppressor mutant was grown in the presence of SDS and fed to mice, it colonized the mouse large intestine. Collectively, the data presented here suggest that BipA may play a role in E. coli MG1655 LPS core biosynthesis and that because MD42 forms clumps in intestinal mucus, it is unable to colonize the mouse large intestine.
机译：E的能力。在小鼠大肠中定殖的大肠杆菌菌株与它们在盲肠和结肠粘液中的生长能力有关。在本研究中，一个 E。用mini-Tn 5 Km（卡那霉素）转座子诱变大肠杆菌 MG1655菌株，并测试了突变体在琼脂平板上生长的能力，其中小鼠盲肠粘液是唯一的碳源和氮。一种突变体，命名为MD42（针对粘液缺陷型），在盲肠粘液琼脂平板上生长较差，但在Luria琼脂平板和葡萄糖最低琼脂平板上生长良好。测序表明，MD42的插入位于 waaQ 基因中，该基因参与脂多糖（LPS）核心的生物合成。就像“深渊”E。大肠杆菌突变体MD42对十二烷基硫酸钠（SDS），胆汁盐和疏水性抗生素Novobiocin过敏。此外，它的LPS核心寡糖被截断，就像一个深粗糙的突变体一样。 MD42最初在链霉素处理的小鼠的大肠中生长，但随后未能定居（每克粪便<10 2 CFU），而其亲本定居在10 7 和每克粪便10 8 CFU。当小鼠盲肠粘膜切片与 E杂交时。大肠杆菌特异的rRNA探针MD42在盲肠粘液中在喂食后24小时观察到团块，而其亲本几乎只以单细胞形式存在，这表明团块可能在防止MD42定植中起作用。令人惊讶的是，在直接从小鼠盲肠分离的未稀释的高粘度盲肠粘液中，MD42的生长几乎与其亲本一样，并且与它的亲本一样，在到达静止期后仍然存活良好，这表明粘液中没有抗微生物剂可以阻止MD42定居。经过mini-mariner 转座子诱变后，分离出MD42的SDS抗性抑制突变体。 mini-mariner 插入片段显示在 E的已知调节子 bipA 基因中。大肠表面成分。当在Luria肉汤中生长时，抑制突变体的LPS核心仍被截断;然而，当抑制突变体在SDS存在下生长时，LPS核心不会被截短。此外，当抑制突变体在SDS存在下生长并喂食给小鼠时，它就定居在小鼠大肠中。总体而言，此处提供的数据表明BipA可能在 E中起作用。大肠埃希菌MG1655 LPS核心生物合成，并且因为MD42在肠道粘液中形成团块，所以它无法在小鼠大肠中定殖。

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