Bile stress response in Listeria monocytogenes LO28:: Adaptation, cross-protection, and identification of genetic loci involved in bile resistance
Bile stress response in Listeria monocytogenes LO28:: Adaptation, cross-protection, and identification of genetic loci involved in bile resistance
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DOI：
10.1128/aem.68.12.6005-6012.2002
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发表时间：
2002-12-01
影响因子：
4.4
通讯作者：
Hill, C
中科院分区：
文献类型：
--
作者：
Begley, M;Gahan, CGM;Hill, C
胆汁是单核细胞增生李斯特菌在人类胃肠道中必须克服的许多障碍之一，以便感染和引起疾病。我们证明了L。单核细胞增多症LO 28能够耐受远远超过体内所遇到的浓度的牛、猪和人胆汁和胆汁酸。与其它临床分离株相比，菌株LO 28具有较强的耐胆汁性。单核细胞增多症，以及无害李斯特菌、肠道沙门氏菌血清型鼠伤寒LT 2和清酒乳杆菌。而指数相L.单核细胞增多性LO 28细胞对未结合的胆汁酸非常敏感，在适应亚致死水平的胆汁酸或异源应激（如酸、热、盐或十二烷基硫酸钠（SDS））之前，显著增强了胆汁抗性。这种适应性反应是独立的蛋白质合成，并在胆汁和SDS适应的情况下，发生在几秒钟内。为了确定与L.单核细胞增多症LO 28、转座子（Tn 917）和质粒（pORI 19）整合库中筛选胆汁敏感突变体。被破坏的基因包括炭疽芽孢杆菌中荚膜形成所需的capA基因座的同源物;编码转录调节因子GADR的基因;参与类异戊二烯生物合成的大肠杆菌基因lytB的同源物;编码枯草芽孢杆菌膜蛋白YxiO的同源物的基因;以及编码在pH稳态中具有推定作用的氨基酸转运蛋白gadE的基因。有趣的是，所有已鉴定的基因座在维持细胞被膜或应激反应中发挥假定的作用。
Bile is one of many barriers that Listeria monocytogenes must overcome in the human gastrointestinal tract in order to infect and cause disease. We demonstrated that stationary-phase cultures of L. monocytogenes LO28 were able to tolerate concentrations of bovine, porcine, and human bile and bile acids well in excess of those encountered in vivo. Strain LO28 was relatively bile resistant compared with other clinical isolates of L. monocytogenes, as well as with Listeria innocua, Salmonella enterica serovar Typhimurium LT2, and Lactobacillus sakei. While exponential-phase L. monocytogenes LO28 cells were exquisitely sensitive to unconjugated bile acids, prior adaptation to sublethal levels of bile acids or heterologous stresses, such as acid, heat, salt, or sodium dodecyl sulfate (SDS), significantly enhanced bile resistance. This adaptive response was independent of protein synthesis, and in the cases of bile and SDS adaptation, occurred in seconds. In order to identify genetic loci involved in the bile tolerance phenotype of L. monocytogenes LO28, transposon (Tn917) and plasmid (pORI19) integration banks were screened for bile-sensitive mutants. The disrupted genes included a homologue of the capA locus required for capsule formation in Bacillus anthracis; a gene encoding the transcriptional regulator ZurR; a homologue of an Escherichia coli gene, lytB, involved in isoprenoid biosynthesis; a gene encoding a homologue of the Bacillus subtilis membrane protein YxiO; and a gene encoding an amino acid transporter with a putative role in pH homeostasis, gadE. Interestingly, all of the identified loci play putative roles in maintenance of the cell envelope or in stress responses.