Groisman E A, Parra-Lopez C, Salcedo M, Lipps C J, Heffron F
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110.
Proc Natl Acad Sci U S A. 1992 Dec 15;89(24):11939-43. doi: 10.1073/pnas.89.24.11939.
The production of antibacterial peptides is a host defense strategy used by various species, including mammals, amphibians, and insects. Successful pathogens, such as the facultative intracellular bacterium Salmonella typhimurium, have evolved resistance mechanisms to this ubiquitous type of host defense. To identify the genes required for resistance to host peptides, we isolated a library of 20,000 MudJ transposon insertion mutants of a virulent peptide-resistant S. typhimurium strain and screened it for hypersensitivity to the antimicrobial peptide protamine. Eighteen mutants had heightened susceptibility to protamine and 12 of them were characterized in detail. Eleven mutants were attenuated for virulence in vivo when inoculated into BALB/c mice by the intragastric route, and 8 of them were also avirulent following intraperitoneal inoculation. The mutants fell into different phenotypic classes with respect to their susceptibility to rabbit defensin NP-1, frog magainin 2, pig cecropin P1, and the insect venom-derived peptides mastoparan and melittin. The resistance loci mapped to eight distinct locations in the genome. Characterization of the mutants showed that one had a defective lipopolysaccharide and another mutant harbored a mutation in phoP, a locus previously shown to control expression of Salmonella virulence genes. Our data indicate that the ability to resist the killing effect of host antimicrobial peptides is a virulence property and that several resistance mechanisms operate in S. typhimurium.
抗菌肽的产生是包括哺乳动物、两栖动物和昆虫在内的各种物种所采用的一种宿主防御策略。成功的病原体，如兼性胞内细菌鼠伤寒沙门氏菌，已经进化出对这种普遍存在的宿主防御类型的抗性机制。为了鉴定对宿主肽产生抗性所需的基因，我们分离了一个由20,000个毒力肽抗性鼠伤寒沙门氏菌菌株的MudJ转座子插入突变体组成的文库，并筛选其对抗菌肽鱼精蛋白的超敏性。18个突变体对鱼精蛋白的敏感性增强，其中12个被详细表征。当通过胃内途径接种到BALB/c小鼠体内时，11个突变体在体内的毒力减弱，其中8个在腹腔接种后也无毒力。这些突变体在对兔防御素NP-1、青蛙蛙皮素2、猪天蚕素P1以及昆虫毒液衍生肽mastoparan和蜂毒素的敏感性方面属于不同的表型类别。抗性基因座定位于基因组中的八个不同位置。对突变体的表征表明，一个突变体的脂多糖有缺陷，另一个突变体在phoP中存在突变，phoP是一个先前已证明可控制沙门氏菌毒力基因表达的基因座。我们的数据表明，抵抗宿主抗菌肽杀伤作用的能力是一种毒力特性，并且鼠伤寒沙门氏菌存在几种抗性机制。
