Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China; Department of Bioengineering, School of Food Science and Bioengineering, Tianjin Agricultural University, Tianjin 300072, P. R. China; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, P. R. China.
Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, P. R. China; Zhejiang Shaoxing Research Institute of Tianjin University, Shaoxing 312300, P. R. China.
J Dairy Sci. 2021 Sep;104(9):9556-9569. doi: 10.3168/jds.2021-20184. Epub 2021 Jun 17.
ComX can improve bacterial competence by modulating global gene expression. Although competence induction may also be a protective mechanism under stress, this has not been investigated in detail. Here, we demonstrated that ComX improved the acid tolerance and nisin yield of Lactococcus lactis, which is an important gram-positive bacterium increasingly used in modern biotechnological applications. We found that overexpression of comX could improve the survival rate up to 36.5% at pH 4.0, compared with only 5.4% and 1.1% with the wild-type and comX knockout strains, respectively. Moreover, quantitative real-time PCR results indicated that comX overexpression stimulated the expression of late competence genes synergistically with exposure to acid stress. Finally, electrophoretic mobility shift assay demonstrated the binding of purified ComX to the cin-box in the promoters of these genes. Taken together, our results reveal a regulation mechanism by which ComX and acid stress can synergistically modulate the expression of late competence genes to enhance cells' acid tolerance and nisin yield.
ComX 可以通过调节全局基因表达来提高细菌的感受态。尽管感受态诱导也可能是应激下的一种保护机制，但这尚未得到详细研究。在这里，我们证明 ComX 可以提高乳球菌（Lactococcus lactis）的耐酸性和乳链菌肽产量，乳球菌是一种在现代生物技术应用中越来越重要的革兰氏阳性菌。我们发现，与野生型和 comX 敲除株相比，comX 过表达可将 pH 值为 4.0 时的存活率提高至 36.5%，而野生型和 comX 敲除株的存活率分别为 5.4%和 1.1%。此外，实时定量 PCR 结果表明，ComX 过表达与酸胁迫协同刺激晚期感受态基因的表达。最后，凝胶电泳迁移率变动分析表明，纯化的 ComX 与这些基因启动子中的 cin-box 结合。总之，我们的结果揭示了 ComX 和酸胁迫可以协同调节晚期感受态基因表达以增强细胞耐酸性和乳链菌肽产量的调控机制。
