Division of Infectious Diseases, Department of Pediatrics, University of Iowa Children's Hospital, 200 Hawkins Drive, Iowa City, IA 52242, USA.
Microb Pathog. 2010 Jun;48(6):230-8. doi: 10.1016/j.micpath.2010.03.006. Epub 2010 Mar 19.
Enterotoxigenic Escherichia coli (ETEC) strains are leading causes of childhood diarrhea in developing countries. ETEC pili and non-pili adherence factors designated colonization surface antigens (CSA) are believed to be important in the pathogenesis of diarrhea. Longus, a type IV pilus identified as the CSA(21), is expressed in up to one-third of ETEC strains, and share similarities to the toxin-coregulated pilus of Vibrio cholerae, and the bundle-forming pilus of enteropathogenic E. coli. To identify longus phenotype and possible function, a site-directed mutation of the lngA major subunit gene in the E9034A wild type ETEC strain was constructed. Lack of longus expression from the lngA mutant was demonstrated by immunoblot analysis and electron microscopy using specific anti-LngA antibody. Formation of self-aggregates by ETEC was shown to be dependent on longus expression as the lngA mutant or wild type grown under poor longus expression conditions was unable to express this phenotype. Longus-expressing ETEC were also associated with improved survival when exposed to antibacterial factors including lysozyme and antibiotics. This suggests that longus-mediated bacterial self-aggregates protect bacteria against antimicrobial environmental agents and may promote gut colonization.
肠产毒性大肠杆菌（ETEC）菌株是发展中国家儿童腹泻的主要原因。ETEC 菌毛和非菌毛附着因子被认为是腹泻发病机制中的重要因素。被认为是 CSA(21)的长型菌毛是一种 IV 型菌毛，在多达三分之一的 ETEC 菌株中表达，与霍乱弧菌的毒素调节菌毛和肠致病性大肠杆菌的束形成菌毛有相似之处。为了鉴定长型菌毛的表型和可能的功能，构建了 E9034A 野生型 ETEC 菌株中 lngA 主要亚基基因的定点突变。通过免疫印迹分析和使用特异性抗 LngA 抗体的电子显微镜观察，证明了 lngA 突变体中长型菌毛的缺失。实验表明，ETEC 的自聚集形成依赖于长型菌毛的表达，因为在 lngA 突变体或在低长型菌毛表达条件下生长的野生型均无法表达这种表型。当 ETEC 暴露于包括溶菌酶和抗生素在内的抗菌因子时，表达长型菌毛的 ETEC 也能提高存活率。这表明长型菌毛介导的细菌自聚集可以保护细菌免受抗菌环境因素的影响，并可能促进肠道定植。
