Microbial shifts of the silkworm larval gut in response to lettuce leaf feeding

Silkworm (Bombyx mori L.) larvae were used as an ideal animal protein source for astronauts in the bioregenerative life support system (BLSS). Here, we compared the difference in bacterial communities of the silkworm larval gut between the BLSS rearing way (BRW) and the traditional rearing way (TRW) through culture-dependent approach, 16S rRNA gene analysis, and denaturing gradient gel electrophoresis (DGGE). The culture-dependent approach revealed that the numbers of gut bacteria of silkworm in the BRW significantly decreased compared with that of the TRW. The analysis of clone libraries showed that the gut microbiota in the BRW was significantly less diverse than that in the TRW. Acinetobacter and Bacteroides were dominant populations in the BRW, and Bacillus and Arcobacter dominated in the TRW. DGGE profiles confirmed the difference of silkworm gut bacterial community between two rearing ways. These results demonstrate that gut bacteria change from the BRW contributes to the decrease of silkworm physiological activity. This study increases our understanding of the change of silkworm gut microbiota in response to lettuce leaf feeding in the BRW. We could use the dominant populations to make probiotic products for nutrient absorption and disease prevention in the BLSS to improve gut microecology, as well as the yield and quality of animal protein.