Quorum sensing (QS) in Aeromonas hydrophila is mainly based on the modulation of ahyI/R genes that regulates bacterial virulence determinant phenotypes. The use of QS inhibitors would be of particular interest in inhibiting bacterial pathogenicity and infections. In this study, we aimed to determine the effect of curcumin, a natural component of Curcuma longa, on the expression of QS regulating genes, ahyI and ahyR, as well as some QS regulated virulence characteristics in pathogenic fish isolated A. hydrophila strains. The minimum inhibitory concentration (MIC) of curcumin against bacteria was determined using the broth micro-dilution method and the expression of quorum sensing genes ahyI and ahyR among the bacteria treated with curcumin was determined using quantitative polymerase chain reaction (qPCR). Also, the effect of curcumin on some QS associated traits, including biofilm formation, swarming and swimming motility, proteolytic potential, and bacterial hemolytic activity was investigated. According to the results, curcumin, at a concentration of 32 µg/mL, significantly reduced the expression of both ahyI and ahyR genes among bacterial strains up to 64.2 and 91.0%, respectively. Moreover, curcumin efficiently inhibited bacterial biofilm formation, swimming, and swarming motility. Also, bacterial proteolytic activity was slightly reduced, while hemolytic activity was not significantly affected. This study demonstrated the use of curcumin to attenuate ahyI/R QS genes and several QS associated phenotypes in A. hydrophila. These findings indicate the therapeutic potential of curcumin as an anti-QS agent, to be used against A. hydrophila pathogenesis in aquaculture.

中文翻译：

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姜黄素对致病性嗜水气单胞菌鱼分离株ahyI/R群体感应基因表达及相关表型的影响

嗜水气单胞菌中的群体感应 (QS) 主要基于调节细菌毒力决定子表型的 ahyI/R 基因。QS 抑制剂的使用在抑制细菌致病性和感染方面具有特别的意义。在这项研究中，我们旨在确定姜黄素（姜黄的天然成分）对 QS 调节基因 ahyI 和 ahyR 表达的影响，以及致病鱼分离的嗜水 A. 菌株中一些 QS 调节的毒力特征。采用肉汤微量稀释法测定姜黄素对细菌的最小抑菌浓度 (MIC)，并采用定量聚合酶链反应 (qPCR) 测定姜黄素处理的细菌中群体感应基因 ahyI 和 ahyR 的表达。还，研究了姜黄素对一些 QS 相关性状的影响，包括生物膜形成、蜂群和游泳运动、蛋白水解潜力和细菌溶血活性。根据结果​​，浓度为 32 µg/mL 的姜黄素显着降低了细菌菌株中 ahyI 和 ahyR 基因的表达，分别高达 64.2% 和 91.0%。此外，姜黄素有效抑制细菌生物膜形成、游泳和蜂群运动。此外，细菌蛋白水解活性略有降低，而溶血活性没有显着影响。该研究证明了姜黄素用于减弱嗜水曲霉中 ahyI/R QS 基因和几种与 QS 相关的表型。这些发现表明姜黄素作为抗 QS 药物的治疗潜力，可用于治疗 A.