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Dynamics of the intestinal bacterial community in black soldier fly larval guts and its influence on insect growth and development.

Black soldier fly (BSF), Hermetia illucens (Diptera: Stratiomyidae), is a prominent insect for its bioconversion of various organic wastes. As a saprotrophic insect, the BSF inhabits microbe-rich environments. However, the influences of the intestinal microorganisms on BSF growth and development are not very clear. In this study, the dynamics of intestinal bacterial community of the BSF larvae were analyzed using pyrosequencing. Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria were the most prevalent bacterial phyla in the intestines of all larval instars. The dynamic changes in bacterial community compositions among different larval instars were striking at the genus level. Klebsiella, Clostridium, Providencia and Dysgonomonas were the relatively most abundant bacteria in the 1st- to 4th-instar BSF larvae, respectively. Dysgonomonas and Providencia also dominated the 5th- and 6th-instar larvae, at ratios of 31.1% and 47.2%, respectively. In total, 148 bacterial strains affiliated with 20 genera were isolated on different media under aerobic and anaerobic conditions. Among them, six bacteria, BSF1-6, were selected for further study. The inoculation of the six isolates independently into the germ-free BSF larvae feeding on an artificial diet showed that all the bacteria, except BSF4, significantly promoted BSF growth and development compared with the germ-free control. Providencia, Citrobacter, Klebsiella, Ochrobactrum and Dysgonomonas promoted BSF development significantly by increasing the weight gains of larvae and pupae, as well as increasing the prepupae and eclosion rates. In addition, Providencia, Citrobacter and Klebsiella shortened BSF life cycle significantly. The results illustrate the promotive effects of intestinal bacteria on BSF growth and development. This article is protected by copyright. All rights reserved.