In the heart of Shandong Agricultural University, a groundbreaking discovery is unfolding that could revolutionize the sericulture industry. Researchers, led by Dr. Chunjiu Ren from the Department of Sericulture, have found that the probiotic Bacillus subtilis significantly enhances the growth and silk production of silkworms (Bombyx mori) reared on artificial diets. This research, published in the journal *Animal Microbiome* (translated as “Animal Microbiome”), not only sheds light on the intricate relationship between gut microbiota and insect growth but also opens new avenues for optimizing artificial diet systems in the sericulture industry.
Silkworms reared on artificial diets often exhibit reduced growth performance and lower silk production compared to those fed on mulberry leaves. This discrepancy is largely attributed to the reduced gut microbial diversity in artificially fed silkworms. Dr. Ren and his team hypothesized that supplementing the artificial diet with B. subtilis, a probiotic known for its benefits in livestock and aquaculture, could improve the silkworms’ growth and health.
The results were striking. Silkworms fed a diet supplemented with B. subtilis showed a significant increase in body weight, with improvements ranging from 9.1% to 22.1% during the larval stages. Moreover, the feed utilization efficiency (FUE) improved by 4.09% to 6.80%, indicating that the silkworms were not only growing faster but also converting their food more efficiently. Cocoon quality metrics also saw notable enhancements, with a 9.77% increase in cocoon shell weight in females and a 6.56% improvement in the cocoon shell ratio.
Dr. Ren explained, “Our findings demonstrate that B. subtilis can modulate the gut microbiota and metabolic pathways in silkworms, leading to improved growth and silk production. This is a significant step forward in our understanding of how probiotics can influence insect health and productivity.”
The research revealed that B. subtilis did not permanently colonize the silkworm midgut but instead transiently modulated gut physiology. It elevated the pH of the midgut fluid and enhanced the activities of key digestive enzymes such as α-amylase, trypsin, and lipase. This modulation of gut physiology is crucial for improving nutrient absorption and overall growth.
Furthermore, 16S rRNA sequencing showed that B. subtilis supplementation reduced gut microbial diversity and altered the community structure. Notably, there was a decrease in the abundance of potential pathogens like Pseudomonas and commensals like Lactobacillus. This shift in gut microbiota composition is believed to contribute to the improved health and growth of the silkworms.
One of the most intriguing findings was the significant increase in phenylalanine levels in the hemolymph, the insect equivalent of blood. Targeted metabolomics identified a 3.1-fold increase in phenylalanine, which is linked to the upregulation of aromatic amino acid metabolism pathways. To confirm the role of phenylalanine, the researchers supplemented the diet with 0.4% phenylalanine and observed similar growth promotion effects, underscoring the pivotal role of this amino acid in host-microbe interactions.
Dr. Ren added, “The elevation of phenylalanine levels and the subsequent upregulation of aromatic amino acid metabolism pathways highlight the complex interplay between gut microbiota and host metabolism. This research not only advances our understanding of insect physiology but also provides practical applications for the sericulture industry.”
The implications of this research are far-reaching. By optimizing artificial diet systems with probiotics like B. subtilis, sericulture farmers can enhance silkworm growth and silk production, leading to increased profitability and sustainability. This study also paves the way for further research into the role of gut microbiota in other insects and potentially other animals, offering new insights into the broader field of animal nutrition and health.
As the sericulture industry continues to evolve, the integration of probiotics and advanced dietary supplements could become a standard practice, driven by the need for more efficient and sustainable production methods. Dr. Ren’s research is a testament to the power of interdisciplinary collaboration, combining microbiology, nutrition, and insect physiology to address real-world challenges.
In the words of Dr. Ren, “This is just the beginning. The potential applications of probiotics in agriculture are vast, and we are excited to explore how these findings can be translated into practical solutions for farmers and the industry as a whole.”
As the world looks towards more sustainable and efficient agricultural practices, the insights gained from this research could very well shape the future of sericulture and beyond. The journey of a silkworm, it seems, is not just a tale of transformation but also a story of innovation and discovery.