Isolation, identification, and positive effects of potential probiotics on Carassius auratus

Abstract

Probiotics, as one of the effective alternatives to antibiotics, could be beneficial to the host. Here we isolated different probiotic candidates from the intestine of Carassius auratus and evaluated their positive effects. Three probiotic candidates (C35, C28, and C19) were isolated. Two of them (C28 and C19) were commonly considered pathogens, been identified as Enterobacter asburiae and Aeromonas veronii, respectively. And C35 was identified as Bacillus tequilensis. In order to evaluate the effects of bacteria supplemented diets on C. auratus, no probiotics (negative control, NC), Bacillus subtilis (positive control, PC) and three probiotic candidates were supplemented in diet, respectively. Compared with NC, the results showed that no significant improvement was found in the three treatments among growth performance and hematology, but we found the three probiotic candidates could promote innate immune and digestion. Interestingly, C28 and C19 showed positive effects on the height of intestinal plica and were conducive to absorption. The results of intestinal microbiota diversity displayed that the potential pathogens such as Aeromonas and Plesiomonas were reduced significantly in all treatments, with potential probiotics like Cetobacterium, Akkermansia, and Romboutsia increasing. Moreover, C28 and C19 could advance the survival rates following A. hydrophila challenge. However, effects of C35 on C. auratus were inconspicuous. Overall, this study screens out three potential probiotics by preliminary experiments that could support the application of probiotics in the future.