霍乱弧菌甘露醇PTS操纵子中mtlR为转录抑制基因

Transcriptional repressor gene——mtlR of mannitol PTS operon in Vibrio cholerae

产毒和非产毒的El Tor生物型霍乱弧菌对甘露醇发酵利用的速率有明显差别,在霍乱致病株的快速判断中有重要的参考价值。通过比较快发酵菌株(非产毒株)和慢发酵菌株(产毒株)mtlR缺失突变株与野生株在含0.2%甘露醇的M9培养液及甘露醇发酵液中生长、产酸等的变化,定性地证明了mtlR基因的抑制作用;另外通过定量RT-PCR进一步验证了MtlR蛋白在mtlCBA转录水平发挥负调控作用。但是mtlR还不是引起快慢发酵菌株对甘露醇发酵差异的直接原因。本研究也为我们研究霍乱弧菌甘露醇快慢发酵差异机制提供了必要的参考依据。

The fermentation rates of mannitol in toxigenic and non-toxigenic El Tor strains of Vibrio cholerae are obviously different, which is a valuable indicator in the rapid identification of toxigenic strain. To determine the regulating role of mtlR in transcription of mannitol PTS operon in V. cholerae, and whether it plays a role in the ferment difference of the toxigenic and non-toxigenic strains, the mtlR deletion mutants from the mannitol rapid-ferment strain （non-toxigenic strain） and slow-ferment strain （toxigenic strain） were constructed. Comparisons of the growth in M9 containing 0.2% mannitol as the sole carbon source and pH change in mannitol fermentation media of these wild strains and their mutants, indicated that nulR is a repressor. Its repression in mtlCBA transcription was further verified with the analyses of quantitative reverse-transcriptional PCR. However, the regulation of mtlR is not the immediate cause of the ferment difference of the toxigenic and non-toxigenic strains. The study also provides the necessary data in the analyses of mannitol ferment difference between the toxigenic and non-toxigenic V. cholerae strains.