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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >The sigma factor σ~s affects antibiotic production and biological control activity of Pseudomonas fluorescens Pf-5
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The sigma factor σ~s affects antibiotic production and biological control activity of Pseudomonas fluorescens Pf-5

机译：σ因子影响荧光假单胞菌Pf-5的抗生素产生和生物防治活性

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摘要

Pseudomonas fluorescens Pf-5, a rhizosphere-inhabiting bacterium that suppresses several soilborne pathogens of plants, produces the antibiotics pyrrolnitrin, pyolu-teorin, and 2,4-diacetylphloroglucinol. A gene necessary for pyrrolnitrin production by Pf-5 was identified as rpoS, which encodes the stationary-phase sigma factor σ~s. Several pleio-tropic effects of an rpoS mutation in Escherichia coli also were observed in an RpoS~- mutant of Pf-5. These included sensitivities of stationary-phase cells -to stresses imposed by hydrogen peroxide or high salt concentration. A plasmid containing the cloned wild-type rpoS gene restored pyrrolnitrin production and stress tolerance to the RpoS~- mutant of Pf-5. The RpoS~- mutant overproduced pyoluteorin and 2,4-diacetylphloroglucinol, two antibiotics that inhibit growth of the phytopathogenic fungus Pythium ultimum, and was superior to the wild type in suppression of seedling damping-off of cucumber caused by Pythium ultimum. When inoculated onto cucumber seed at high cell densities, the RpoS~- mutant did not survive as well as the wild-type strain on surfaces of developing seedlings. Other stationary-phase-specific pheno-types of Pf-5, such as the production of cyanide and extracellular protease(s) were expressed by the RpoS~- mutant, suggesting that σ~s is only one of the sigma factors required for the transcription of genes in stationary-phase cells of P. fluorescens. These results indicate that a sigma factor encoded by rpoS influences antibiotic production, biological control activity, and survival of P. fluorescens on plant surfaces.
机译：荧光假单胞菌Pf-5是一种根际居住细菌，可抑制植物的几种土壤传播的病原体，可产生吡咯硝菌素，pyolu-teorin和2,4-二乙酰基间苯三酚。 Pf-5产生吡咯硝菌素必需的基因被鉴定为rpoS，它编码固定相σσs。在Pf-5的RpoS-突变体中也观察到了大肠杆菌中rpoS突变的多效性效应。这些包括固定相细胞对过氧化氢或高盐浓度施加的应力的敏感性。含有克隆的野生型rpoS基因的质粒恢复了吡咯硝菌素的产生和对Pf-5的RpoS-突变体的胁迫耐受性。 RpoS〜-突变体过量生产了pylututeorin和2,4-diacetylphloroglucinol，这两种抗生素可抑制植物致病真菌终极腐霉菌的生长，并且在抑制由终极腐霉菌引起的黄瓜减苗方面优于野生型。当以高细胞密度接种到黄瓜种子上时，RpoS〜-突变株在野生幼苗表面上的存活率不及野生型菌株。 Pf-5的其他固定相特异性表型（如氰化物和细胞外蛋白酶的产生）由RpoS〜-突变体表达，表明σ〜s仅是Pf-5所需的sigma因子之一。荧光假单胞菌固定相细胞中基因的转录。这些结果表明，由rpoS编码的sigma因子会影响抗生素的产生，生物学控制活性以及植物表面荧光假单胞菌的存活。

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