Genomic insights, determination of quorum quenching potential of a beta-lactamase enzyme from Chromohalobacter sp. strain D23 against Aeromonas hydrophila and molecular docking study.

Biofilm formation and other virulence phenotypes under quorum sensing regulation play a vital role in the pathogenicity of Aeromonas hydrophila, triggering the emergence of multi-drug resistance (MDR) which increases fish mortality, environmental issues, and economic loss in aquaculture, necessitating the discovery of novel drugs to bypass standard antibiotics. Here, quorum quenching (QQ) may be a sustainable anti-virulent approach. β-Lactamase enzyme obtained from Chromohalobacter sp. strain D23 restricted violacein pigmentation in Chromobacterium violaceum CV026 by degrading C4-homoserine lactone (C4-HSL) and C6-HSL up to 70% (P < 0.0001). HPLC study also revealed > 73% enzymatic breakdown of both C4-HSL and C6-HSL within 2 h. Crude β-lactamase also hampered biofilm formation of A. hydrophila by reducing total biomass (> 66%, P < 0.001) and cellular viability (62%, P < 0.0001) without affecting planktonic growth. QS-mediated other virulence factors of A. hydrophila, like hemolysin, serine protease, exopolysaccharides, metalloprotease, and lipase activities, were also significantly inhibited (P < 0.0001). Draft genome size of strain D23 was 3.6 mb, having 64.01% G + C content. Annotation revealed the presence of a MBL (metallo-beta-lactamase)-fold metallo-hydrolase enzyme. Multiple sequence alignment indicated the presence of the conserved HXHXDH domain. Pairwise alignment showed 65% ≤ sequence identity with known marine lactonase enzymes. The molecular docking study revealed moderate binding affinity of β-lactamase to C4-HSL and C6-HSL (- 5.3 kcal/mol). Thus, the present study shows the potent QQ activity of β-lactamase of strain D23 against MDR A. hydrophila, targeting their pathogenesis without necessarily killing them, which can minimize the use of antibiotics in aquaculture and also suggests possible biomedical use. This study also highlights the usefulness of less explored marine bacteria as a potent source of bioactive enzymes.