Molecular Identification and Phylogenetic Characterization of Lignocellulose-Degrading Gut Bacteria Isolated From the Eri Silkworm (Samia cynthia ricini)

Abstract

Objective: The present study was aimed at identifying and characterising lignocellulose-degrading bacterial isolates from the gut of the eri silkworm, Samia cynthia ricini, by 16S rRNA gene sequencing and phylogenetic analysis. Methods: Genomic DNA was isolated from six bacterial isolates and PCR amplified for the 16S rRNA gene. The amplified products were sequenced and aligned with reference sequences available in the NCBI GenBank database using BLAST analysis. Multiple sequence alignment was performed, and phylogenetic relationships were deduced using the Neighbour-Joining method with 1000 bootstrap replicates in MEGA11. Results: Sequence analysis revealed that the isolates are Bacillus paralicheniformis (BUBSL1, 99.2%), Bacillus subtilis (BUBSL2, 99.5%), Bacillus licheniformis (BUBSL3, 98.9%), Paenibacillus sp. (BUBSL4, 97.8%), Bacillus velezensis (BUBSL5, 99.3%) and Paenibacillus lactis (BUBSL6, 99.0%). Phylogenetic analysis grouped the isolates into the genera Bacillus and Paenibacillus, supporting their taxonomic position and evolutionary relationship, and the clustering pattern showed that the isolates were closely related to the reference strains obtained from GenBank. Conclusion: The gut microbiota of Samia cynthia ricini is composed of diverse bacterial species predominantly from the genera Bacillus and Paenibacillus. The isolated strains are potential lignocellulose-degrading bacteria, which can be used for future biofuel-related studies and may assist in biomass conversion.