Department of Applied and Environmental Microbiology, School of Life Sciences, Ludong University, Yantai 264025, P.R. China.
The Affiliated Hospital of Ludong University, Yantai 264000, P.R. China.
J Microbiol Biotechnol. 2019 Aug 28;29(8):1299-1309. doi: 10.4014/jmb.1904.04029.
As an opportunistic bacterial pathogen, PAO1 contains two phenazineproducing gene operons, () and (), each of which is independently capable of encoding all enzymes for biosynthesizing phenazines, including phenazine-1-carboxylic acid and its derivatives. Other previous study reported that the RpoS-deficient mutant SS24 overproduced pyocyanin, a derivative of phenazine-1- carboxylic acid. However, it is not known how RpoS mediates the expression of two operons and regulates pyocyanin biosynthesis in detail. In this study, with deletion of the gene in the PAΔ mutant and the PAΔ mutant respectively, we demonstrated that RpoS exerted opposite regulatory roles on the expression of the and operons. We also confirmed that the operon played a critical role and especially biosynthesized much more phenazines than the operon when the gene was knocked out in . By constructing the translational reporter fusion vector - and the chromosomal fusion mutant PAΔ::, we verified that RpoS deficiency caused increased expression of , a transcription regulator gene in a first quorum sensing system () that activates overexpression of the operon, suggesting that in the absence of RpoS, LasR might act as an intermediate in overproduction of phenazine biosynthesis mediated by the operon in .
作为一种机会性病原体，PAO1 含有两个吩嗪产生基因操纵子（）和（），每个操纵子都能够独立编码合成吩嗪的所有酶，包括吩嗪-1-羧酸及其衍生物。其他先前的研究表明，RpoS 缺陷型 SS24 突变体过度产生了绿脓菌素，这是吩嗪-1-羧酸的衍生物。然而，目前尚不清楚 RpoS 如何详细调节两个操纵子的表达并调节绿脓菌素生物合成。在这项研究中，通过在 PAΔ 突变体和 PAΔ 突变体中分别缺失基因，我们证明了 RpoS 对和操纵子的表达具有相反的调节作用。我们还证实，当在 PAΔ 中敲除基因时，操纵子在绿脓菌素生物合成中发挥了关键作用，尤其是合成了比操纵子更多的吩嗪。通过构建翻译报告融合载体和染色体融合突变体 PAΔ::，我们验证了 RpoS 缺乏导致转录调节基因的表达增加，这是第一个群体感应系统（）中的一个基因，该系统激活了操纵子的过度表达，表明在缺乏 RpoS 的情况下，LasR 可能在 操纵子介导的吩嗪生物合成的过度产生中充当中间物。
