Affiliated Hospital, Ludong University, Yantai 264025, China.
Department of Applied and Environmental Microbiology, School of Life Sciences, Ludong University, Yantai 264000, China.
Microb Pathog. 2020 Oct;147:104409. doi: 10.1016/j.micpath.2020.104409. Epub 2020 Jul 21.
Pyocyanin, a main virulence factor that is produced by Pseudomonas aeruginosa, plays an important role in pathogen-host interaction during infection. Two copies of phenazine-biosynthetic operons on genome, phz1 (phzA1B1C1D1E1F1G1) and phz2 (phzA2B2C2D2E2F2G2), contribute to phenazine biosynthesis. In our previous study, we found that RpoS positively regulates expression of the phz2 operon and pyocyanin biosynthesis in P. aeruginosa PAO1. In this work, when a TetR-family regulator gene, pip, was knocked out, we found that pyocyanin production was dramatically reduced, indicating that Pip positively regulates pyocyanin biosynthesis. With further phenazines quantification and β-galactosidase assay, we confirmed that Pip positively regulates phz2 expression, but does not regulate phz1 expression. In addition, while the rpoS gene was deleted, expression of pip was down-regulated. Expression of rpoS in the wild-type PAO1 strain, however, was similar to that in the Pip-deficient mutant PAΔpip, suggesting that expression of pip could positively be regulated by RpoS, whereas rpoS could not be regulated by Pip. Taken together, we drew a conclusion that Pip might serve as an intermediate in RpoS-modulated expression of the phz2 operon and pyocyanin biosynthesis in P. aeruginosa.
绿脓菌素是铜绿假单胞菌产生的主要毒力因子，在感染过程中病原体与宿主的相互作用中起着重要作用。基因组上有两个吩嗪生物合成操纵子，phz1（phzA1B1C1D1E1F1G1）和 phz2（phzA2B2C2D2E2F2G2），有助于吩嗪的生物合成。在我们之前的研究中，我们发现 RpoS 正向调节铜绿假单胞菌 PAO1 中 phz2 操纵子和绿脓菌素生物合成的表达。在这项工作中，当敲除 TetR 家族调节基因 pip 时，我们发现绿脓菌素的产生显著减少，表明 Pip 正向调节绿脓菌素的生物合成。通过进一步的吩嗪定量和β-半乳糖苷酶测定，我们证实 Pip 正向调节 phz2 的表达，但不调节 phz1 的表达。此外，当 rpoS 基因缺失时，pip 基因的表达下调。然而，野生型 PAO1 菌株中的 rpoS 基因表达与 Pip 缺陷型 PAΔpip 中的 rpoS 基因表达相似，表明 pip 的表达可以被 RpoS 正向调节，而 rpoS 不能被 Pip 调节。综上所述，我们得出结论，Pip 可能作为 RpoS 调节铜绿假单胞菌 phz2 操纵子和绿脓菌素生物合成表达的中间物。
