Pyoverdines Are Essential for the Antibacterial Activity of Pseudomonas chlororaphis YL-1 under Low-Iron Conditions

文献类型： 外文期刊

第一作者： Liu, Youzhou

作者： Liu, Youzhou;Zhou, Yaqiu;Qiao, Junqing;Tang, Bao;Zhang, Rongshen;Liu, Yongfeng;Liu, Youzhou;Lu, Shi-En;Dai, Chen;Yu, Wenjie

作者机构：

关键词： Pseudomonas chlororaphis; pyoverdine; low-iron; antibacterial; Xanthomonas oryzae pv. oryzae

期刊名称：APPLIED AND ENVIRONMENTAL MICROBIOLOGY （ 影响因子：4.016； 五年影响因子：4.597 ）

ISSN： 0099-2240

年卷期： 2021 年 87 卷 7 期

页码：

收录情况： SCI

摘要： Pseudomonas chlororaphis YL-1 has extensive antimicrobial activities against phytopathogens, and its genome harbors a pyoverdine (PVD) biosynthesis gene cluster. The alternative sigma factor PvdS in Pseudomonas aeruginosa PAO1 acts as a critical regulator in response to iron starvation. The assembly of the PVD backbone starts with peptide synthetase enzyme PvdL. PvdF catalyzes formylation of L-OH-Orn to produce L-N-5-hydroxyornithine. Here, we describe the characterization of PVD production in YL-1 and its antimicrobial activity in comparison with that of its PVD-deficient Delta pvdS, Delta pvdF, and Delta pvdL mutants, which were obtained using a sacB-based site-specific mutagenesis strategy. Using in vitro methods, we examined the effect of exogenous iron under low-iron conditions and an iron-chelating agent under iron-sufficient conditions on PVD production, antibacterial activity, and the relative expression of the PVD transcription factor gene pvdS in YL-1. We found that strain YL-1, the Delta pvdF mutant, and the Delta pvdS(pUCP26-pvdS) complemented strain produced visible PVDs and demonstrated a wide range of inhibitory effects against Gram-negative and Gram-positive bacteria in vitro under low-iron conditions and that with the increase of iron, its PVD production and antibacterial activity were reduced. The antibacterial compounds produced by strain YL-1 under low-iron conditions were PVDs based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Moreover, the antibacterial activity observed in vitro was correlated with in vivo control efficacies of strain YL-1 against rice bacterial leaf blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae. Collectively, PVDs are responsible for the antibacterial activities of strain YL-1 under both natural and induced low-iron conditions. IMPORTANCE The results demonstrated that PVDs are essential for the broad-spectrum antibacterial activities of strain YL-1 against both Gram-positive and Gram-negative bacteria under low-iron conditions. Our findings also highlight the effect of exogenous iron on the production of PVD and the importance of this bacterial product in bacterial interactions. As a biocontrol agent, PVDs can directly inhibit the proliferation of the tested bacteria in addition to participating in iron competition.

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