Abstract
Gram-negative bacteria utilize N-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 Ruegeria mobilis YJ3, isolated from healthy shrimp, showed strong AHLs degradative activity. In the current study, an AHL lactonase (designated RmmL) was cloned and characterized from Ruegeria mobilis 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 Pseudomonas aeruginosa PAO1, while for the violacein and the extracellular protease activities by Chromobacterium violaceum CV026 and Vibrio anguillarum VIB72, no significant reduction was observed. This study suggests that RmmL might be used as a therapeutic agent in aquaculture.
Highlights
Quorum sensing (QS), known as “auto-induction”, was originally found in Vibrio fisheri [1].quorum sensing (QS) is a bacterial cell-to-cell communication system, in which bacteria regulate gene expression in the environment in accordance with cell density by using diffusible signal molecules
High-performance liquid chromatography analysis indicated that RmmL works as an acylhomoserine lactones (AHLs) lactonase catalyzing AHL
This study suggests that RmmL might be used as a therapeutic agent in aquaculture
Summary
QS is a bacterial cell-to-cell communication system, in which bacteria regulate gene expression in the environment in accordance with cell density by using diffusible signal molecules. By bacterial communication, QS can regulate gene expression and harmonize their behaviors including biofilm formation, bioluminescence, antibiotic production, and virulence factor secretion. Many different types of QS molecules were identified including N-acylhomoserine lactones (AHLs), autoinducer-2 (AI-2), 2-heptyl-3-hydroxy-4-quinoline (Pseudomonas quinolone signal, PQS), and 2-heptyl-4(1H)-hydroxyquinoline, HHQ) [2]. AHLs and AI-2 are the two most studied types. Quorum quenching (QQ) can disrupt the QS communication system by enzymatic degradation of signal molecules. These enzymes might be sorted into three major categories
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