Nowadays, microbial infections have caused increasing economic losses in aquaculture industry and deteriorated worldwide environments. Many of these infections are caused by opportunistic pathogens through cell-density mediated quorum sensing (QS). The disruption of QS, known as quorum quenching (QQ), is an effective and promising way to prevent and control pathogens, driving it be the potential bio-control agents. In our previous studies, AHL lactonase AiiK was identified with many characteristics, and constitutive expression vector pELX1 was constructed to express heterologous proteins in Lactobacillus casei MCJΔ1 (L. casei MCJΔ1). In this study, recombinant strain pELCW-aiiK/L. casei MCJΔ1 (LcAiiK) and wild-type Aeromonas hydrophila (A. hydrophila) were co-cultured to test the QQ ability of LcAiiK against A. hydrophila. A cell wall-associated expression vector pELCW for L. casei MCJΔ1 was constructed. Localization assays revealed that the expressed AiiK was anchored at the surface layer of LcAiiK via vector pELCW-aiiK. LcAiiK (OD600 = 0.5) degraded 24.13 μM of C6-HSL at 2 h, 40.99 μM of C6-HSL at 12 h, and 46.63 μM of C6-HSL at 24 h. Over 50% LcAiiK cells maintained the pELCW-aiiK plasmid after 15 generations of cultivation without erythromycin. Furthermore, LcAiiK inhibited the swimming motility, extracellular proteolytic activity, haemolytic activity and biofilm formation of A. hydrophila AH-1 and AH-4. The AHL lactonase AiiK is firstly and constitutively expressed at the surface layer of L. casei MCJΔ1. LcAiiK displayed considerable AHL lactonase activity and great QQ abilities against A. hydrophila AH-1 and AH-4 by attenuating their QS processes instead of killing them. Therefore, the LcAiiK can be exploited as an anti-pathogenic drug or a bio-control agent to control the AHL-mediated QS of pathogenic bacteria.

中文翻译：

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干酪乳杆菌MCJΔ1异源表达AHL内切酶AiiK，对嗜水气单胞菌AH-1和AH-4具有很强的群体猝灭能力

如今，微生物感染已导致水产养殖业的经济损失日益增加，全球环境恶化。这些感染中的许多感染是由机会致病菌通过细胞密度介导的群体感应（QS）引起的。QS的破坏（称为群体淬灭（QQ））是一种有效且有前途的预防和控制病原体的方法，使其成为潜在的生物防治剂。在我们以前的研究中，已鉴定出具有许多特征的AHL内酯酶AiiK，并构建了组成型表达载体pELX1以在干酪乳杆菌MCJΔ1（干酪乳杆菌MCJΔ1）中表达异源蛋白。在这项研究中，重组菌株pELCW-aiiK / L。共同培养caseiMCJΔ1（LcAiiK）和野生型嗜水气单胞菌（A. hydrophila），以测试LcAiiK对嗜水曲霉的QQ能力。构建了干酪乳杆菌MCJΔ1的细胞壁相关表达载体pELCW。定位测定表明，表达的AiiK通过载体pELCW-aiiK锚定在LcAiiK的表面层。LcAiiK（OD600 = 0.5）在2 h时降解了24.13μM的C6-HSL，在12 h时降解了40.99μM的C6-HSL，在24 h时降解了46.63μM的C6-HSL。在不使用红霉素培养15代后，超过50％的LcAiiK细胞保持了pELCW-aiiK质粒。此外，LcAiiK抑制了嗜水链球菌AH-1和AH-4的游泳运动，细胞外蛋白水解活性，溶血活性和生物膜形成。AHL内酯酶AiiK首先和组成性表达在干酪乳杆菌MCJΔ1的表层。LcAiiK显示出相当大的AHL内酯酶活性和强大的QQ抗A能力。通过减弱QS进程而不是杀死它们来亲水AH-1和AH-4。因此，LcAiiK可以用作抗病原药或生物控制剂来控制AHL介导的病原细菌QS。