Betts J, Finlay B B
Department of Biochemistry, University of British Columbia, Vancouver, Canada.
Can J Microbiol. 1992 Aug;38(8):852-7. doi: 10.1139/m92-138.
Salmonella typhimurium is capable of entering into (invading) nonphagocytic host cells. To systematically identify the bacterial genes necessary for this process, 15,000 Tn10dCm random transposon mutants of S. typhimurium were individually screened for invasiveness, using the human colonic epithelial Caco-2 cell line. Four hundred and eighty-eight mutants had decreased levels of invasiveness; most were nonmotile. However, five mutants, representing four loci, were completely motile. Further characterization of these five mutants showed that they were also unable to enter the dog kidney epithelial cell line MDCK and the mouse macrophage line J774.A1. In contrast to the parental strain, they were unable to disrupt the transepithelial resistance of polarized epithelial monolayers, nor were they able to penetrate across these epithelial barriers. Three of the four classes of mutants remained virulent in mice. The results confirm several aspects of S. typhimurium invasiveness: (i) intact motility enhances invasiveness of cultured cells; (ii) S. typhimurium invasiveness is multifactorial, and at least six distinct genetic loci are involved; and (iii) invasion loci involved in uptake into epithelial cells are also needed for uptake into cultured phagocytic cells. The results also emphasize that decreased levels of invasiveness eliminate bacterial penetration of polarized epithelial barriers and invasiveness loci mutants are not necessarily avirulent.
鼠伤寒沙门氏菌能够进入（侵袭）非吞噬性宿主细胞。为了系统地鉴定这一过程所需的细菌基因，利用人结肠上皮Caco-2细胞系对15000个鼠伤寒沙门氏菌的Tn10dCm随机转座子突变体进行了侵袭性筛选。488个突变体的侵袭水平降低；大多数是非运动性的。然而，代表四个位点的五个突变体是完全运动性的。对这五个突变体的进一步表征表明，它们也无法进入犬肾上皮细胞系MDCK和小鼠巨噬细胞系J774.A1。与亲本菌株相比，它们无法破坏极化上皮单层的跨上皮电阻，也无法穿透这些上皮屏障。四类突变体中的三类在小鼠中仍具毒性。结果证实了鼠伤寒沙门氏菌侵袭性的几个方面：（i）完整的运动性增强培养细胞的侵袭性；（ii）鼠伤寒沙门氏菌的侵袭性是多因素的，至少涉及六个不同的基因位点；（iii）进入上皮细胞所需的侵袭位点对于进入培养的吞噬细胞也是必需的。结果还强调，侵袭水平的降低消除了细菌对极化上皮屏障的穿透，侵袭位点突变体不一定无毒。
