Insight into the gut microbiology of wild-caught Mangrove Red Snapper, Lutjanus argentimaculatus (Forsskal, 1775)

Abstract

Documenting bacteria present in healthy individuals forms the first step in understanding the effects of microbial manipulation in aquaculture systems. Among the commensal microflora, gut microbiota has attracted extensive attention owing to their role in host metabolism and health maintenance. Basic knowledge on normal gut microbes within a particular host species is thus essential to determine how successfully these microbes can be manipulated and engineered for sustainable aquaculture systems. In spite of the good aquaculture potential of Mangrove red snapper, Lutjanus argentimaculatus, the information on microbial communities associated with the gut of this fish, and their contribution towards digestive efficiency and disease resistance is scarce. Therefore, an attempt was made to elucidate the abundance and diversity of cultivable gut microbes of wild caught L. argentimaculatus along with their digestive exoenzyme profiles and prohibitory effect against fish pathogens. Results on abundance showed similar gut bacterial loads as that of other marine fish imposing the less contribution of microflora to the volume of gut materials in fish. Eleven distinct bacterial species including two proposed novel vibrios were identified. An incidental observation of Morganella morganii throughout samples is an alarming signal, emphasizing the need for immediate de-gutting to avoid histamine intoxication. Abundance of digestive enzyme producers and excellent enzymatic potential of some isolates suggested the contribution of digestive enzymes may supplement to the symbiosis between gut flora and host and the information is of interest to aquaculture nutritionists/commercial industries. Interestingly, some isolates demonstrated estimable co-aggregation with aquatic pathogens, indicating their involvement in disease resistance and the results correlated well with gut microbial diversity. These findings highlight the significant role of gut microbes towards nutritional physiology and disease resistance of this aquaculture candidate in natural ecosystem. The culturable microbiota profiles of wild fish generated in the study can be applied for measuring the quality of husbandry routines in aquaculture facility of this marine fish. Overall, the present study fetches insights on the gut microbiome of healthy L. argentimaculatus which forms a platform for follow-up studies. The study may also help in the development of “functional” fish feeds for L. argentimaculatus. The investigation also demonstrated some potential digestive enzyme-producing isolates having probiotic applications in commercial aquaculture.