Advancing aquaculture probiotic discovery via an innovative protocol for isolation of indigenous, heat and salt tolerant, quorum quenching probiotic candidates

Our study isolated 24 bacterial isolates, 11 demonstrating quorum quenching (QQ) activity by degrading HHL, indicating potential for antivirulence therapy. Among these, eight were non-hemolytic, suggesting safety in the presence of host wounds. Six non-hemolytic isolates exhibited proteolytic activity, which is essential for aiding protein digestion. Whole genome sequencing revealed their identity as <i>Priestia megaterium</i> PMUG01 and PMUG02, <i>Lysinibacillus fusiformis</i> LFUG, <i>Micrococcus yunnanensis MYUG</i>, and two novel species tentatively named <i>Kocuria crassamentum species nova</i> strain KSNUG, and <i>Heyndrickxia crassamentum species nova</i> strain HSNUG. Despite some virulence-associated genes, none of the strains demonstrated pathogenicity in <i>Artemia</i> nauplii. Apart from an <i>lsaB</i> gene in <i>P. megaterium</i>, which confers resistance to lincosamides, no antibiotic resistance genes were detected. Our findings highlight these strains' biosafety and probiotic potential for aquaculture, offering promising candidates for sustainable disease management and improved feed utilization in farmed species. These results pave the way for developing indigenous and effective, non-antibiotic-based probiotic solutions to mitigate disease risks in aquaculture.