Abstract：
Pyrroloquinoline quinone (PQQ) is a redox cofactor with numerous important physiological functions, and the type VI secretion system (T6SS) is commonly found in Gram-negative bacteria and plays important roles in physiological metabolism of the bacteria. In this study, we found that the deletion of pqqF enhanced the secretion of Hcp-1 in Serratia marcesens FS14 in M9 medium. Transcriptional analysis showed that the deletion of pqqF almost had no effect on the expression of T6SS-1. Further study revealed that the increased secretion of Hcp-1 was altered by the pH changes of the culture medium through the reaction catalyzed by the glucose dehydrogenases in FS14. Finally, we demonstrated that decreased pH of culture medium has similar inhibition effects as PQQ induced on the secretion of T6SS-1. This regulation mode on T6SS by pH in FS14 is different from previously reported in other bacteria. Therefore, our results suggest a novel pH regulation mode of T6SS in S. marcesens FS14, and would broaden our knowledge on the regulation of T6SS secretion.
摘要：
吡咯喹啉醌(PQQ)是一种具有许多重要生理功能的氧化还原辅因子,VI型分泌系统（T6SS）常见于革兰氏阴性菌中，在细菌的生理代谢中起着重要作用。在这项研究中,我们发现pqqF的缺失增强了M9培养基中粘质沙雷氏菌FS14中Hcp-1的分泌。转录分析表明，pqqF的缺失对T6SS-1的表达几乎没有影响。进一步的研究表明，通过FS14中葡萄糖脱氢酶催化的反应，培养基的pH变化改变了Hcp-1的分泌增加。最后,我们证明，培养基的pH值降低对T6SS-1的分泌具有与PQQ诱导的相似的抑制作用。FS14中pH对T6SS的这种调节模式与以前报道的其他细菌不同。因此,我们的研究结果提示了一种新的pH调节模式T6SS在MarcesensFS14中，并将拓宽我们对T6SS分泌调节的认识。
