Lo Reggie Y C, Sathiamoorthy Sarmitha, Shewen Patricia E
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
FEMS Microbiol Lett. 2006 Dec;265(1):18-25. doi: 10.1111/j.1574-6968.2006.00460.x. Epub 2006 Sep 19.
The expression of Mannheimia haemolytica A1 genes during in vivo growth was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) using total RNA extracted directly from M. haemolytica A1 recovered from pneumonic lungs of cattle. Primers specific for three groups of genes were used. Group 1 includes virulence-related genes: lktC, tbpB, ahs, nmaA, gs60 and gcp. Group 2 includes genes that code for putative two-component regulatory systems: narP, narQ, ttrR, ttrS, phoB and phoR. Group 3 includes genes involved in regular cellular functions such as plp4, thiL and rrf. The RT-PCR data were examined in conjunction with the percent pneumonic lesion in each lung scored during necropsy. The analysis showed that lungs with a higher percent pneumonic score exhibit expression of more M. haemolytica A1 genes. For group 1 genes, lktC was expressed in the majority of samples, whereas the other genes were only expressed in some samples. This was not unexpected as the leukotoxin is a major virulence factor of the bacterium. The genes encoding the response regulators for the putative two-component regulatory systems were found to be expressed in more samples than the genes encoding the sensor proteins. The regulator proteins may be required in higher levels to regulate expression of target genes.
利用从患肺炎牛肺中分离得到的溶血曼氏杆菌A1直接提取的总RNA，通过逆转录聚合酶链反应（RT-PCR）检测溶血曼氏杆菌A1基因在体内生长过程中的表达情况。使用了针对三组基因的特异性引物。第1组包括与毒力相关的基因：lktC、tbpB、ahs、nmaA、gs60和gcp。第2组包括编码假定双组分调节系统的基因：narP、narQ、ttrR、ttrS、phoB和phoR。第3组包括参与正常细胞功能的基因，如plp4、thiL和rrf。RT-PCR数据与尸检时每只肺的肺炎病变百分比一起进行分析。分析表明，肺炎评分百分比越高的肺，溶血曼氏杆菌A1基因的表达越多。对于第1组基因，大多数样本中都表达lktC，而其他基因仅在一些样本中表达。这并不意外，因为白细胞毒素是该细菌的主要毒力因子。发现编码假定双组分调节系统应答调节因子的基因比编码传感蛋白的基因在更多样本中表达。调节蛋白可能需要更高水平来调节靶基因的表达。
