Beneficial effects of four Bacillus strains on the larval cultivation of Litopenaeus vannamei

We studied the effects of four strains of Bacillus isolated from the guts of healthy wild adult shrimp on survival and rate of development of whiteleg shrimp Litopenaeus vannamei larvae to understand how endemic Bacillus probiotic strains improve the health of larvae. This included bacterial isolation, assays of hemolytic activity, antagonism against pathogenic Vibrio species, growth, and adhesion to shrimp intestinal mucus, and molecular identification. Bacillus strains were tested on larval shrimp using a daily concentration of 1 × 105 CFU mL–1, starting each bioassay at nauplii V at a density of 225 nauplii L− 1. Inoculations of four natural, commercial products and antibiotic oxytetracycline were added directly to the water. All treatments induced a significant increase in survival compared to the control, with strain YC5-2 showing the highest survival (~ 67%), followed by AlibioMR (~ 57%). A mix of two strains induced the highest rate of development (7.00), followed by AlibioMR (6.35). The results showed remarkable antagonistic activity by the four non-hemolytic Bacillus strains against Vibrio campbelli, V. vulnificus, V. parahaemolyticus, and V. alginolyticus and the potential and efficiency of probiotics isolated from shrimp gut to improve survival of shrimp larvae.

► Four strains of Bacillus isolated from adult shrimp L. vannamei, enhanced survival and rate of development of shrimp larvae.
► Bacillus strains isolated from the shrimp L. vannamei, showed antagonism against Vibrio campbelli, V. vulnificus, V. parahaemolyticus, and V. alginolyticus.
► Probiotic strains adhered and grow in shrimp intestinal mucosa.
► The highest larval survival was registered with the strain YC5-2 followed by a commercial probiotic.