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.

绿脓杆菌（Pseudomonas aeruginosa）产生的主要致病因子-花青素在感染过程中与病原体-宿主相互作用中起着重要作用。基因组上的吩嗪生物合成操纵子的两个副本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可以正向调节铜绿假单胞菌PAO1中phz2操纵子的表达和绿脓素的生物合成。在这项工作中，当TetR的家族调节基因，PIP被敲除后，我们发现黄体生成素显着降低，这表明Pip积极调节黄素的生物合成。通过进一步的吩嗪定量和β-半乳糖苷酶测定，我们证实了Pip阳性调节phz2表达，但不调节phz1表达。此外，尽管rpoS基因被删除，但pip的表达却被下调。的表达的rpoS在野生型菌株PAO1，然而，是类似于在PIP缺陷型突变PAΔ PIP，提示的表达PIP能积极通过RPOS来调节，而的rpoS无法由Pip监管。综上所述，我们得出的结论是，Pip可能是铜绿假单胞菌中RpoS调节的phz2操纵子和pyyocyanin生物合成的RpoS调节表达的中间体。