Studies on the adhesion, aggregative properties and the probiotic efficiency of a potent bacteriocin-producing shrimp gut isolateBacillus subtilissubsp.inaquosorumV1againstCarassius auratus

Bacterial adhesion is considered as an important property that enables probiotic bacteria to colonise the gastrointestinal tract and confer a health benefit to the host. In the present study, a shrimp gut isolateBacillus subtilissubsp.inaquosorumV(1), an efficient producer of bacteriocin was used. Autoaggregation, co-aggregation and cell surface hydrophobicity assays were performed to confirm the aggregating phenotype of the strain. The results of the assays showed that the strain belonged to a strong aggregating phenotype, autoaggregation (45.7%) and co-aggregation with the pathogens likeE. coli(33.17%) andS. aureus(35.7%). It also aggregates with the hydrocarbons such as xylene (44.8%) and toluene (52.67%). The effect of LiCl(2)on bacterial cells indicated the role of S-layer proteins on the bacterial adhesion in which LiCl2-treated cells showed minimal adhesion (16.47%), when compared with untreated cells (45.3%). The candidate strain was supplemented in a commercial fish feed and fed to the ornamental fishCarassius auratus.After 30 days, the experimental group of fishes showed an increase in weight gain (34.56%) with the SGR of 0.99% than the control group. The enzymes to toxify the respiratory oxidative stress, namely SOD, catalase and the digestive enzyme activity were found to be more in the experimental fishes. Similarly, the total protein content of the experimental fishes showed a marked increase than the control diet-fed fish. The above results inferred that the experimental strain has the better adhesive property and can be used as an effective probiotic to improve the production in aquaculture.