Dynamic Alterations of the Intestinal Microbiota of Fifth-Instar Silkworms (Bombyx mori) Fed an Artificial Diet or Mulberry Leaves

• Published in: Insects (Basel, Switzerland) Switzerland), 2024-12, Vol.15 (12), p.970
• Main Authors: Chen, Chuanjie, Li, Meng, Li, Feng, Liang, Xiaoyan, Zhang, Haiyang, Gu, Yinyu, Guo, Guang
• Format: Article
• Language: English
• Subjects: artificial diet; Artificial diets; Bacteria; Bombyx mori; Cocoons; Community structure; Diet; Digestive system; dynamic alterations; Efficiency; Females; Food; Gastrointestinal tract; Insects; intestinal microbiota; Intestinal microflora; Leaves; Microbiota; Microorganisms; mulberry leaves; Nutrient deficiency; Physiology; Probiotics; silkworm; Silkworms
• ISSN: 2075-4450; 2075-4450
• DOI: 10.3390/insects15120970

Intestinal microbes are known to impact the growth and development of insects. However, there are few reports on the intestinal microbiota of silkworms (Bombyx mori). The present study used Illumina 16S rRNA gene sequencing to investigate the changes over time in the intestinal bacteriome of fifth-instar silkworms fed mulberry leaf (MB) or artificial diet (AD). The results showed that the intestinal microbiota richness was significantly higher, before the 4th day of the fifth instar, in the silkworms fed AD rather than MB, while the richness was consistent between the AD and MB groups directly before cocooning. Proteobacteria was the most dominant phylum in MBs, AD, and the silkworm intestinal bacteriome, regardless of sex, feed type, or date, except that Firmicutes was the most dominant phylum for females on the 6th day of the fifth instar. Acinetobacter was the dominant genus in silkworms fed MB, while Enterococcus was the dominant genus in silkworms fed AD. Only 3.62% of the intestinal microbiota of silkworms fed MB was derived from MB, while 13.71% of the intestinal microbiota of silkworms fed AD was derived from AD. Thus, both bacterial communities were dominated by bacteria of unknown origin (non-feed sources). In the correlation network analysis, the silkworms fed AD appeared to have more complex interactions than the silkworms fed MB. Proteobacteria was the phylum most closely related to silkworm cocoon quality and feeding efficiency. Pantoea was the genera most closely related to cocoon quality and silkworm feeding efficiency in silkworms fed MB. AD had a significant impact on the predicted functions of the intestinal microbiota. There were significant differences in all six KEGG level 1 functions and all BugBase (except for Gram_Positive) phenotypes between silkworms fed AD or MB. The BugBase “Aerobic” phenotype was significantly higher in females compared to males, in both the AD and MB groups, while the “Oxidative_Stress_Tolerant” phenotype was the opposite. Overall, the findings suggest that the diversity, community structure, and predicted functions of intestinal bacteria in silkworms were significantly influenced by feed type. The study provides insights into the complex silkworm intestinal bacterial diversity and a foundation for probiotic screening.