Whitehead Kristi, Versalovic James, Roos Stefan, Britton Robert A
Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
Appl Environ Microbiol. 2008 Mar;74(6):1812-9. doi: 10.1128/AEM.02259-07. Epub 2008 Feb 1.
Probiotic bacteria encounter various stresses after ingestion by the host, including exposure to the low pH in the stomach and bile in the small intestine. The probiotic microorganism Lactobacillus reuteri ATCC 55730 has previously been shown to survive in the human small intestine. To address how L. reuteri can resist bile stress, we performed microarray experiments to determine gene expression changes that occur when the organism is exposed to physiological concentrations of bile. A wide variety of genes that displayed differential expression in the presence of bile indicated that the cells were dealing with several types of stress, including cell envelope stress, protein denaturation, and DNA damage. Mutations in three genes were found to decrease the strain's ability to survive bile exposure: lr1864, a Clp chaperone; lr0085, a gene of unknown function; and lr1516, a putative esterase. Mutations in two genes that form an operon, lr1584 (a multidrug resistance transporter in the major facilitator superfamily) and lr1582 (unknown function), were found to impair the strain's ability to restart growth in the presence of bile. This study provides insight into the possible mechanisms that L. reuteri ATCC 55730 may use to survive and grow in the presence of bile in the small intestine.
益生菌被宿主摄入后会遇到各种应激，包括暴露于胃中的低pH值和小肠中的胆汁。益生菌罗伊氏乳杆菌ATCC 55730此前已被证明能在人类小肠中存活。为了研究罗伊氏乳杆菌如何抵抗胆汁应激，我们进行了微阵列实验，以确定该微生物暴露于生理浓度胆汁时发生的基因表达变化。在胆汁存在下表现出差异表达的多种基因表明，细胞正在应对几种类型的应激，包括细胞膜应激、蛋白质变性和DNA损伤。发现三个基因的突变会降低菌株在胆汁暴露下的存活能力：lr1864，一种Clp伴侣蛋白；lr0085，一个功能未知的基因；以及lr1516，一种假定的酯酶。发现形成操纵子的两个基因lr1584（主要转运体超家族中的一种多药耐药转运蛋白）和lr1582（功能未知）的突变会损害菌株在胆汁存在下重新开始生长的能力。本研究深入了解了罗伊氏乳杆菌ATCC 55730在小肠胆汁存在下可能用于存活和生长的潜在机制。
