Screening of gastrointestinal bacteria of Indian major carps for a candidate probiotic species for aquaculture practices

Abstract

Probotic selection could be detrimental for the success of aquaculture practices. While, in most of the cases emphasis is given to the production of antibacterial compounds, and in vitro inhibitory activities of a bacterium for choosing a probiotic strain, however, other criteria like non-antibiotic resistant, non-haemolytic nature and non-pathogenic potentiality of probiotic strain are often overlooked. We have screened gastrointestinal bacteria isolated from all the three species of Indian major carps viz., Labeo rohita, Catla catla and Cirrhinus mrigala for a suitable probiotic. Bacteria like Aeromonas (Aeromonas species, A. hydrophila), Micrococcus, Corynebacterium, Plesiomonas, Bacillus (Bacillus species, B. subtilis) and Pseudomonas (Pseudomonas species, P. aeruginosa) exhibited antibacterial activities against different pathogens. Among these, B. subtilis was found to grow at a wider range of temperatures, pH and salt concentrations and was non-haemolytic, non-antibiotic resistant, non-pathogenic and inhibited all the tested primary and secondary pathogens. Dietary supplementation of the bacteria at 108 CFU g−1 feed also enhanced the growth of Indian major carp, L. rohita. Based upon these characteristics, we aimed to develop a suitable probiotic for aquaculture practices.