College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.
College of Veterinary Medicine, Qingdao Agricultural University, Qingdao 266109, China.
Mar Drugs. 2018 Oct 8;16(10):370. doi: 10.3390/md16100370.
Gram-negative bacteria utilize -acylhomoserine lactones (AHLs) as quorum sensing (QS) signaling molecules for intercellular communication. Cell-to-cell communication depends on cell population density, and AHL-dependent QS is related to the production of multiple genes including virulence factors. Quorum quenching (QQ), signal inactivation by enzymatic degradation, is a potential strategy for attenuating QS regulated bacterial infections. Both Gram-positive and -negative bacteria have QQ enzymes that can degrade AHLs. In our previous study, strain YJ3, isolated from healthy shrimp, showed strong AHLs degradative activity. In the current study, an AHL lactonase (designated RmmL) was cloned and characterized from YJ3. Amino acid sequence analysis showed that RmmL has a conserved "HXHXDH" motif and clusters together with lactonase AidC that belongs to the metallo-β-lactamase superfamily. Recombinant RmmL could degrade either short- or long-chain AHLs in vitro. High-performance liquid chromatography analysis indicated that RmmL works as an AHL lactonase catalyzing AHL ring-opening by hydrolyzing lactones. Furthermore, RmmL can reduce the production of pyocyanin by PAO1, while for the violacein and the extracellular protease activities by CV026 and VIB72, no significant reduction was observed. This study suggests that RmmL might be used as a therapeutic agent in aquaculture.
革兰氏阴性菌利用酰基高丝氨酸内酯（AHLs）作为群体感应（QS）信号分子进行细胞间通讯。细胞间通讯取决于细胞群体密度，而 AHL 依赖性 QS 与包括毒力因子在内的多种基因的产生有关。群体感应淬灭（QQ），即通过酶促降解使信号失活，是减弱 QS 调控细菌感染的一种潜在策略。革兰氏阳性菌和革兰氏阴性菌都有可以降解 AHLs 的 QQ 酶。在我们之前的研究中，从健康虾中分离到的菌株 YJ3 表现出强烈的 AHLs 降解活性。在本研究中，从 YJ3 中克隆并表征了一种 AHL 内酯酶（命名为 RmmL）。氨基酸序列分析表明，RmmL 具有保守的“HXHXDH”基序，与属于金属β-内酰胺酶超家族的内酯酶 AidC 聚类在一起。重组 RmmL 可以在体外降解短链或长链 AHLs。高效液相色谱分析表明，RmmL 作为 AHL 内酯酶，通过水解内酯催化 AHL 开环。此外，RmmL 可以降低 PAO1 产生的绿脓菌素，而对 CV026 和 VIB72 的生物发光和胞外蛋白酶活性，没有观察到明显的降低。本研究表明，RmmL 可能在水产养殖中用作治疗剂。
