肺炎链球菌comX基因可影响细菌毒力基因表达

Effect of comX gene on the expression of virulence genes in streptococcus pneumoniae

目的:探讨肺炎链球菌的转化相关基因comX与其毒力表达的关系.方法:采用插入失活的方法制备肺炎链球菌的相关基因缺陷菌株,通过小鼠毒力实验观察它们毒力的变化,并应用RT-PCR测定肺炎链球菌的主要毒力因子透明质酸酶(phd),分泌型IgA结合蛋白(sIgA),肺炎链球菌自溶酶(lytA),肺炎链球菌神经氨酸酶A(nanA)和肺炎链球菌溶血素(ply)在细菌感受态发生过程中的表达,并比较其在野生和缺陷菌株中的表达的异同.结果:野生菌株的毒力基因受感受态刺激因子(CSP)诱导表达增加;虽comX基因缺陷菌株与野生菌株感染小鼠的能力无显著差异,但其ply基因的表达与comE基因缺陷菌株一样显著低于野生菌株的表达.结论:comX可通过细菌转化的通路影响细菌毒力基因的表达.

AIM： To further understand the mechanisms underlying the opportunistic infection of streptococcus pneumort/ae, and to investigate the effect of its transformation-associated gene comX on the expression of its vindence genes. METHODS： Four genedeficient strains comE^- , comX^-, comX1^- and comX2^- were established by the insertion of inactivating gene comE or comX1 or/ and comX2. The virulence of gene-deficient strains were com- pared with the wild ones by challenging mice through intraperitoneal route and by detecting the mRNA expressions of five virulence genes, which were autolysin（lytA）, neuramindase （nanA）, pneumolysin（ ply）, hyaluronidase （ phd ） and secretory IgA binding protein（sIgA）. RESULTS： The mRNA expressions of the five virulence genes in wild strains were induced by competence-stimulating peptide（CSP）. The infection ability of comE^- and comX^- strains was not significantly different from that of the wild strains （ P 〉 0.05 ）, but the mRNA expression of ply gene was reduced in comE^- and comX^- strains compared with wild strains （ P 〈 0.05）. CONCLUSION： Transformation-associated gene comX might affect the mRNA expressions of virulence genes such as phd, lytA, nanA and sIgA in streptococcus pneumoniae through transformation pathway.