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Isolation and characterization of bacteria associated with silkworm gut under antibiotic-treated larval feeding
Abstract:
The impact of antibiotics on growth, cocoon production was assessed in addition to isolation and characterization of bacteria associated with silkworm gut of infected larvae. Larval rearing was maintained at recommended conditions of temperature and humidity. Silkworm larvae showing abnormal symptoms were collected from the control group and dissected for gut collection. Bacteria were isolated from the gut content by spreading on agar plates and incubated at 37 °C for 48 hrs. Bacterial identification and phylogenetic analysis were carried out by 16S rRNA gene sequencing. The isolated bacteria were subjected to antimicrobial susceptibility test (disc diffusion methods) by using Penicillin (10 µg/mL), Tetracycline (30 µg/mL), Amoxicillin (25 µg/mL), Ampicillin (10 µg/mL), and Erythromycin (15 µg/mL). All isolated strains showed positive results for the catalase test. We isolated and identified bacterial strains (n = 06) from the gut of healthy and diseased silkworm larvae. Based on the 16S rRNA gene sequence, isolated bacteria showed close relation with Serratia, Bacillus, and Pseudomonas spp. Notably, 83.3% of strains were resistant to Penicillin, Tetracycline, Amoxicillin, Ampicillin, and Erythromycin but 16.6% showed antibiotic susceptibility to the above-mentioned commonly used antibiotics. Silkworm larvae fed on penicillin-treated leaves showed significant improvement in larval weight, larval length, and cocoon production. Significantly higher larval weight (6.88g), larval length (5.84cm), and cocoon weight (1.33g) were recorded for larvae fed on leaves treated with penicillin as compared to other antibiotics. Isolated bacterial strains showed close relation with Serratia spp., Bacillus spp. and Pseudomonas spp.
Insights
Penicillin treatment significantly improved silkworm growth and cocoon production, despite most gut bacteria showing antibiotic resistance. Penicillin was most effective among tested antibiotics for enhancing silkworm development.
Area of Science:
- Sericulture
- Microbiology
- Animal Science
Background:
- Antibiotic resistance is a growing concern in agriculture and animal husbandry.
- Understanding the gut microbiome of silkworms is crucial for optimizing production and disease management.
Purpose of the Study:
- To assess the impact of antibiotics on silkworm growth and cocoon production.
- To isolate and characterize bacteria from silkworm guts and determine their antibiotic susceptibility.
- To evaluate the efficacy of different antibiotics in improving silkworm development.
Main Methods:
- Isolation and identification of gut bacteria using 16S rRNA gene sequencing.
- Antimicrobial susceptibility testing via disc diffusion method.
- Assessment of silkworm growth parameters (weight, length) and cocoon production after antibiotic treatment.
Main Results:
- Six bacterial strains related to Serratia, Bacillus, and Pseudomonas spp. were identified.
- 83.3% of isolated strains exhibited resistance to common antibiotics (Penicillin, Tetracycline, Amoxicillin, Ampicillin, Erythromycin).
- Penicillin treatment led to significant improvements in larval weight, length, and cocoon production compared to other antibiotics.
Conclusions:
- Penicillin demonstrates a beneficial effect on silkworm growth and cocoon yield, even in the presence of resistant gut bacteria.
- Targeted antibiotic application, like penicillin, can be a viable strategy to enhance sericulture productivity.
- Further research into silkworm gut microbiota and antibiotic interactions is warranted.
