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首页> 外文期刊>Applied Microbiology >Repression of the Antifungal Activity of Pseudomonas sp. Strain DF41 by the Stringent Response
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Repression of the Antifungal Activity of Pseudomonas sp. Strain DF41 by the Stringent Response

机译：假单胞菌sp。的抗真菌活性的抑制。严格响应应变DF41

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The stringent response (SR) enables bacteria to adapt to nutrient limitation through production of the nucleotides guanosine tetraphosphate and guanosine pentaphosphate, collectively known as (p)ppGpp. Two enzymes are responsible for the intracellular pools of (p)ppGpp: RelA acts as a synthetase, while SpoT can function as either a synthetase or a hydrolase. We investigated how the SR affects the ability of the biological control agent Pseudomonas sp. strain DF41 to inhibit the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary. Strain DF41 relA and relA spoT mutants were generated and found to exhibit increased antifungal activity. Strain DF41 produces a lipopeptide (LP) molecule that is essential for Sclerotinia biocontrol. LP production and protease activity were both elevated in the relA and relA spoT mutants. Addition of relA but not spoT in trans restored the mutant phenotype to that of the parent. Next, we investigated whether an association exists between the SR and known regulators of biocontrol, including the Gac system and RpoS. A gacS mutant of strain DF41 produced less (p)ppGpp and exhibited a 1.7-fold decrease in relA expression compared to the wild type, suggesting that relA forms part of the Gac regulon. We discovered that rpoS transcription was reduced significantly in the SR mutants. Furthermore, rpoS provided in trans restored protease activity to wild-type levels but did not attenuate antifungal activity. Finally, relA expression was decreased in the mutants, indicating that the SR is required for maximum expression of relA .
机译：严格应答（SR）使细菌能够通过产生四磷酸鸟苷和五磷酸鸟苷核苷酸（统称为（p）ppGpp）来适应营养限制。两种酶负责（p）ppGpp的细胞内池：RelA充当合成酶，而SpoT可以充当合成酶或水解酶。我们调查了SR如何影响生物控制剂假单胞菌sp。的能力。菌株DF41抑制真菌病原菌Sclerotiorum sclerotiorum（Lib。）de Bary。产生了菌株DF41 relA和relA spoT突变体，发现它们具有增强的抗真菌活性。菌株DF41产生了脂蛋白（LP）分子，对菌核菌的生物防治至关重要。 relA和relA spoT突变体的LP产量和蛋白酶活性均升高。反式添加relA但不添加spoT可将突变表型恢复为亲本的表型。接下来，我们研究了SR和已知的生物控制调节剂（包括Gac系统和RpoS）之间是否存在关联。与野生型相比，菌株DF41的gacS突变体产生的（p）ppGpp更少，并且relA表达降低了1.7倍，这表明relA构成了Gac regulon的一部分。我们发现在SR突变体中rpoS转录显着降低。此外，以反式提供的rpoS将蛋白酶活性恢复至野生型水平，但并未减弱抗真菌活性。最后，在突变体中relA表达降低，表明SR是relA最大表达所必需的。

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