Department of Microbiology, School of Life Sciences, Pondicherry University, Puducherry 605014, India.
Department of Biotechnology, School of Life Sciences, Pondicherry University, Puducherry 605014, India.
J Microbiol Biotechnol. 2020 Apr 28;30(4):571-582. doi: 10.4014/jmb.1907.07030.
Quorum sensing (QS)-mediated infections cause severe diseases in human beings. The control of infectious diseases by inhibiting QS using antipathogenic drugs is a promising approach as antibiotics are proving inefficient in treating these diseases. Marine fungal ( PPR) extract was found to possess effective antipathogenic characteristics. The minimum inhibitory concentration (MIC) of the fungal extract against test pathogen PAO1 was 1,000 μg/ml. Sub-MIC concentrations (250 and 500 μg/ml) of fungal extract reduced QS-regulated virulence phenotypes such as the production of pyocyanin, chitinase, protease, elastase, and staphylolytic activity in PAO1 by 84.15%, 73.15%, 67.37%, 62.37%, and 33.65%, respectively. Moreover, it also reduced the production of exopolysaccharides (74.99%), rhamnolipids (68.01%), and alginate (54.98%), and inhibited the biofilm formation of the bacteria by 90.54%. In silico analysis revealed that the metabolite of PPR binds to the bacterial QS receptor proteins (LasR and RhlR) similar to their respective natural signaling molecules. Cyclo(-Leu-Pro) (CLP) and 4-Hydroxyphenylacetamide (4-HPA) were identified as potent bioactive compounds among the metabolites of PPR using in silico approaches. The MIC values of CLP and 4-HPA against PAO1 were determined as 250 and 125 μg/ml, respectively. All the antivirulence assays were conducted at sub-MIC concentrations of CLP (125 μg/ml) and 4-HPA (62.5 μg/ml), which resulted in marked reduction in all the investigated virulence factors. This was further supported by gene expression studies. The findings suggest that the metabolites of PPR can be employed as promising QS inhibitors that target pathogenic bacteria.
群体感应（QS）介导的感染会导致人类患上严重疾病。通过使用抗病原体药物抑制 QS 来控制传染病是一种很有前途的方法，因为抗生素在治疗这些疾病方面效果不佳。海洋真菌（PPR）提取物被发现具有有效的抗病原体特性。真菌提取物对测试病原体 PAO1 的最小抑菌浓度（MIC）为 1000μg/ml。亚 MIC 浓度（250 和 500μg/ml）的真菌提取物分别将 QS 调节的毒力表型如绿脓菌素、几丁质酶、蛋白酶、弹性蛋白酶和葡萄球菌溶素活性的产生降低了 84.15%、73.15%、67.37%、62.37%和 33.65%。此外，它还降低了细菌胞外多糖（74.99%）、鼠李糖脂（68.01%）和海藻酸盐（54.98%）的产生，并抑制了细菌生物膜的形成，抑制率为 90.54%。计算机分析表明，PPR 的代谢物与细菌 QS 受体蛋白（LasR 和 RhlR）结合的方式类似于它们各自的天然信号分子。使用计算机方法，鉴定出代谢物中的环（亮氨酰-脯氨酸）（CLP）和 4-羟基苯乙酰胺（4-HPA）是有效的生物活性化合物。CLP 和 4-HPA 对 PAO1 的 MIC 值分别确定为 250 和 125μg/ml。所有抗病毒活力测定均在 CLP（125μg/ml）和 4-HPA（62.5μg/ml）的亚 MIC 浓度下进行，结果所有研究的毒力因子均显著减少。基因表达研究进一步证实了这一点。研究结果表明，PPR 的代谢物可以作为有前途的针对病原菌的 QS 抑制剂。
