Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
J Bacteriol. 2020 Jul 9;202(15). doi: 10.1128/JB.00156-20.
Naturally occurring free fatty acids (FFAs) are recognized as potent antimicrobial agents that also affect the production of virulence factors in bacterial pathogens. In the foodborne pathogen , some medium- and long-chain FFAs act as antimicrobial agents as well as signaling compounds, causing a repression of transcription of virulence genes. We previously observed that the master virulence regulator PrfA is involved in both the antimicrobial and virulence-inhibitory response of to selected FFAs, but the underlying mechanisms are presently unknown. Here, we present a systematic analysis of the antimicrobial and PrfA-inhibitory activities of medium- and long-chain FFAs of various carbon chain lengths and degrees of saturation. We observed that exposure to specific antimicrobial and nonantimicrobial FFAs prevented PrfA-dependent activation of virulence gene transcription and reduced the levels of PrfA-regulated virulence factors. Thus, an antimicrobial activity was not compulsory for the PrfA-inhibitory ability of an FFA. binding experiments revealed that PrfA-inhibitory FFAs were also able to prevent the constitutively active variant PrfA* from binding to the PrfA box in the promoter region of the virulence gene , whereas noninhibitory FFAs did not affect its ability to bind DNA. Notably, the unsaturated FFAs inhibited the DNA binding activity of PrfA* most efficiently. Altogether, our findings support a model in which specific FFAs orchestrate a generalized reduction of the virulence potential of by directly targeting the key virulence regulator PrfA. is a Gram-positive pathogen able to cause foodborne infections in humans and animals. Key virulence genes in are activated by the transcription regulator PrfA, a DNA binding protein belonging to the CRP/FNR family. Various signals from the environment are known to affect the activity of PrfA, either positively or negatively. Recently, we found that specific medium- and long-chain free fatty acids act as antimicrobial agents as well as signaling compounds in Here, we show that both antimicrobial and nonantimicrobial free fatty acids inhibit PrfA-dependent activation of virulence gene transcription by interfering with the DNA binding activity of PrfA. Our findings suggest that free fatty acids could be candidates for alternative therapies against .
天然存在的游离脂肪酸（FFAs）被认为是有效的抗菌剂，它们还影响细菌病原体毒力因子的产生。在食源性病原体中，一些中链和长链 FFAs 既是抗菌剂，又是信号化合物，导致毒力基因的转录受到抑制。我们之前观察到，主要毒力调节因子 PrfA 参与了选定 FFAs 对 的抗菌和抑制毒力反应，但目前尚不清楚其潜在机制。在这里，我们对不同碳链长度和饱和度的中链和长链 FFAs 的抗菌和 PrfA 抑制活性进行了系统分析。我们观察到，暴露于特定的抗菌和非抗菌 FFAs 可防止 PrfA 依赖性毒力基因转录的激活，并降低 PrfA 调节的毒力因子水平。因此，一种 FFA 的抗菌活性不是其抑制 PrfA 的能力所必需的。PrfA 结合实验表明，PrfA 抑制性 FFAs 也能够阻止组成型激活变体 PrfA结合到毒力基因启动子区域的 PrfA 盒，而非抑制性 FFAs 不会影响其结合 DNA 的能力。值得注意的是，不饱和 FFAs 最有效地抑制 PrfA的 DNA 结合活性。总的来说，我们的研究结果支持这样一种模型，即特定的 FFAs 通过直接靶向关键毒力调节因子 PrfA，协调调控 毒力潜力的普遍降低。是一种革兰氏阳性病原体，能够引起人类和动物的食源性感染。 中的关键毒力基因由转录调节因子 PrfA 激活，PrfA 是一种属于 CRP/FNR 家族的 DNA 结合蛋白。来自环境的各种信号被认为会影响 PrfA 的活性，无论是正向还是负向。最近，我们发现特定的中链和长链游离脂肪酸在 中既作为抗菌剂，又作为信号化合物。在这里，我们表明，无论是抗菌的还是非抗菌的游离脂肪酸，都通过干扰 PrfA 的 DNA 结合活性，抑制 PrfA 依赖性毒力基因转录的激活。我们的研究结果表明，游离脂肪酸可能是针对 的替代治疗候选物。
