Ogunniyi A David, Giammarinaro Philippe, Paton James C
Department of Molecular Biosciences, Adelaide University, Adelaide, South Australia 5005, Australia1.
Microbiology (Reading). 2002 Jul;148(Pt 7):2045-2053. doi: 10.1099/00221287-148-7-2045.
The polysaccharide capsule of Streptococcus pneumoniae and several well-characterized virulence proteins are known to contribute to the pathogenesis of pneumococcal disease. However, there is a paucity of data on the expression of their respective genes in vivo. In this study, the relative abundance of the mRNA transcripts of the genes encoding pneumolysin (ply), pneumococcal surface protein A (pspA), pneumococcal surface antigen A (psaA) and choline-binding protein A (cbpA), and of the first gene of the capsular polysaccharide biosynthesis locus (cps2A), was measured in virulent type 2 pneumococci harvested from the blood of BALB/c mice at 12 h and 24 h following intraperitoneal infection. The mRNA levels were then compared, using relative quantitative RT-PCR, with those present in organisms grown in serum broth. The expression of ply was upregulated threefold at 12 h, and 10-fold at 24 h post-infection; the expression of pspA and psaA was upregulated threefold and fivefold, respectively, at 12 h post-infection. Interestingly, the expression of pspA was 36-fold higher at 24 h post-infection whereas the expression of cps2A was upregulated approximately fourfold at 12 and 24 h post-infection. However, cbpA mRNA levels remained comparable in vivo and in vitro. When organisms were grown in whole blood or THY broth, the relative expression of these genes in the two growth media also differed markedly. This work provides direct molecular evidence that known virulence-associated genes of S. pneumoniae are differentially expressed in vivo. Data on the relative expression of these genes in different growth media also suggests that the regulation of expression of these genes is highly complex and multifactorial.
已知肺炎链球菌的多糖荚膜和几种特征明确的毒力蛋白与肺炎球菌疾病的发病机制有关。然而，关于它们各自基因在体内表达的数据却很少。在本研究中，测定了编码肺炎溶血素（ply）、肺炎球菌表面蛋白A（pspA）、肺炎球菌表面抗原A（psaA）和胆碱结合蛋白A（cbpA）的基因以及荚膜多糖生物合成位点的第一个基因（cps2A）的mRNA转录本在腹腔感染后12小时和24小时从BALB/c小鼠血液中收获的2型强毒肺炎球菌中的相对丰度。然后，使用相对定量逆转录聚合酶链反应（RT-PCR）将mRNA水平与在血清肉汤中生长的生物体中的水平进行比较。感染后12小时，ply的表达上调了3倍，24小时上调了10倍；感染后12小时，pspA和psaA的表达分别上调了3倍和5倍。有趣的是，感染后24小时pspA的表达高出36倍，而cps2A的表达在感染后12小时和24小时上调了约4倍。然而，cbpA的mRNA水平在体内和体外保持相当。当生物体在全血或THY肉汤中生长时，这些基因在两种生长培养基中的相对表达也有显著差异。这项工作提供了直接的分子证据，表明肺炎链球菌已知的与毒力相关的基因在体内差异表达。关于这些基因在不同生长培养基中相对表达的数据也表明，这些基因表达的调控是高度复杂和多因素的。
