Probiotic Potential Characterization and Unsupervised Algorithmic Cluster Analysis of Lactic Acid Bacteria Isolated from Gut of Channa gachua Fish

This is the first effort in Northeast India to isolate lactic acid bacteria from the gut of Channa gachua and to evaluate their probiotic potential through clustering analysis. The study examined the effectiveness of these bacteria against freshwater pathogens. A variety of tests were conducted, including morphological differentiation, catalase activity, IMViC tests, acid and bile tolerance, auto aggregation and coaggregation, hydrophobicity, hemolytic and biosafety assays, 16S rRNA sequencing for molecular identification, pathogen antagonism, antibiotic susceptibility, growth performance, coexistence tests between the isolated probiotic strains, and antagonism of the consortia against pathogens. Clustering analysis was performed using heat maps and principal component analysis, focusing on the probiotic attributes of the isolates. Among all the isolates, two strains with the most promising probiotic characteristics were identified through Sanger’s dideoxy sequencing of the 16S rRNA gene: Staphylococcus hominis strain BICG1 and Streptococcus equinus strain BICG2. These strains exhibited a high degree of auto aggregation, coaggregation, and hydrophobicity, with their growth unaffected by varying levels of acid and bile. When tested against pathogens Aeromonas hydrophila and Aeromonas jandaei, both Staph. hominis and Strep. equinus strains showed effectiveness. All strains, except for Strep. equinus, were found to be sensitive to four antibiotics. Both strains were compatible, and their consortium displayed enhanced in vitro inhibition against aquatic pathogens. This investigation led to the screening of two potential probiotic strains, Staph. hominis strain BICG1 and Strep. equinus strain BICG2, for use in the aquaculture sector.