Isolation, identification, and evaluation of intestinal bacteria in Macrobrachium rosenbergii

Probiotics are live microbial food supplements that have been shown to have beneficial effects on animal health. Endogenous probiotic bacteria have long been used for their proposed health-promoting properties and have become a hot research topic in growth improvement in aquaculture. The endogenous probiotic bacteria from intestines of Macrobrachium rosenbergii (giant river prawn) was explored for their probiotic potential, from which 367 bacterial strains were isolated from the intestine of M. rosenbergii . After 16S rDNA sequence analysis, 234 isolates were identified as Lactococcus garvieae , which accounted for 63.76% of the total number of culturable intestinal bacteria, suggesting that this bacterium was the main component of the microbiota. Furthermore, to reveal the probiotic properties of L. garvieae , this isolated bacterial strain was characterized morphologically, physiologically, and biochemically. Its enzyme production capacity, bacteriostatic activity, and resistance to acid, high temperature, and pH, were assessed. In vitro experiments showed that the L. garvieae (No. C6a2) had a fast growth rate and entered the logarithmic phase rapidly. Besides, it had characteristics of acid-production and resistance, enzyme-producing capacity, and strong antibacterial activity against pathogenic Staphylococcus aureus, Aeromonas hydrophila , and Aeromonas veronii . However, it lacked the ability to tolerate high temperature. Our results provide novel data to deepen our understanding of the intestinal bacteria structure of M. rosenbergii and valuable information for probiotic screening and the application for M. rosenbergii .