Baker Sarah J, Gunn John S, Morona Renato
Department of Microbiology and Immunology, University of Adelaide, Adelaide, South Australia, Australia 5005.
Department of Microbiology, University of Texas Health Science Centre at San Antonio, 7703 Floyd Curl Dr, San Antonio, TX 78284-7758, USA.
Microbiology (Reading). 1999 Feb;145 ( Pt 2):367-378. doi: 10.1099/13500872-145-2-367.
Salmonella typhi is the causative agent of typhoid fever in humans. A cell-culture based assay involving the human monocyte macrophage cell line U937 has been developed to examine S. typhi invasion and survival. An S. typhi PhoP- (null) mutant was shown to be restricted in net growth in phorbol myristate acetate (PMA) differentiated U937 (PMA-U937) cells, and an S. typhi PhoPc (constitutive) mutant showed a defect in invasion. Neither of the phoP/Q mutants were growth impaired in HeLa cells, however the PhoPc mutant was impaired in invasion. As opposed to what was found for S. typhi, Salmonella typhimurium wild-type, PhoP- and PhoPc mutants grew equally well in PMA-U937 cells, indicating that the PhoP(-)-mediated net growth restriction in the PMA-U937 cells was S. typhi specific. An S. typhi mutation, pqaB::MudJ, recently shown to be a PhoP-activated locus, was shown to have a net growth defect in PMA-U937 cells. Sequencing of the S. typhipqaB gene revealed it had 98% identity to the fifth gene in a S. typhimurium PmrA/B regulated operon necessary for 4-aminoarabinose lipid A modification and polymyxin B resistance. The pqaB locus was regulated by PmrA/B (whose activity is modulated by PhoP-PhoQ) and the pqaB transposon mutant was sensitive to polymyxin B. The lipopolysaccharides (LPS) of S. typhi and S. typhimurium wild-type, PhoP- and PhoPc mutants, were compared by SDS-PAGE and silver staining. Differences in the LPS profile between the two Salmonella species were observed, and shown to be affected differently by the PhoPc mutation. Additionally, the pqaB::MudJ mutation affected S. typhi LPS. The effects on LPS may have ramifications for the difference between S. typhi and S. typhimurium infection of hosts.
伤寒沙门氏菌是人类伤寒热的病原体。已开发出一种基于细胞培养的检测方法，该方法涉及人类单核细胞巨噬细胞系U937，用于检测伤寒沙门氏菌的侵袭和存活情况。一株伤寒沙门氏菌PhoP（缺失）突变体在佛波酯肉豆蔻酸酯（PMA）分化的U937（PMA-U937）细胞中的净生长受到限制，而一株伤寒沙门氏菌PhoPc（组成型）突变体在侵袭方面存在缺陷。phoP/Q突变体在HeLa细胞中生长均未受损，然而PhoPc突变体在侵袭方面受损。与伤寒沙门氏菌的情况相反，鼠伤寒沙门氏菌野生型、PhoP和PhoPc突变体在PMA-U937细胞中生长情况相同，这表明PhoP（-）介导的PMA-U937细胞中的净生长限制是伤寒沙门氏菌特有的。最近显示为PhoP激活位点的伤寒沙门氏菌突变体pqaB::MudJ，在PMA-U937细胞中存在净生长缺陷。对伤寒沙门氏菌pqaB基因的测序显示，它与鼠伤寒沙门氏菌PmrA/B调节操纵子中的第五个基因具有98%的同一性，该操纵子对于4-氨基阿拉伯糖脂质A修饰和多粘菌素B抗性是必需的。pqaB位点受PmrA/B调节（其活性由PhoP-PhoQ调节），pqaB转座子突变体对多粘菌素B敏感。通过SDS-PAGE和银染比较了伤寒沙门氏菌和鼠伤寒沙门氏菌野生型、PhoP和PhoPc突变体的脂多糖（LPS）。观察到两种沙门氏菌之间LPS谱的差异，并表明PhoPc突变对其影响不同。此外，pqaB::MudJ突变影响伤寒沙门氏菌的LPS。对LPS的影响可能对伤寒沙门氏菌和鼠伤寒沙门氏菌感染宿主的差异产生影响。
