A Chitinase Gene Belonging to Serratia marcescens GBS19 Reveals Horizontal Gene Transfer within Bacterial Strains Besides its Biocontrol Potential Against Myzus persicae.

Microorganisms produce diverse enzymes with applications in biological control and pest management. Chitinase enzymes degrade chitin, a structural component of insect exoskeletons and fungal cell walls, offering sustainable and environmentally friendly solutions for agricultural pest and pathogen management. This study focused on the chiA gene from our original strain belonging to Serratia marcescens identified using multi locus sequencing and ribosomal DNA analysis, amplified via PCR, cloned into expression vectors, and expressed as a recombinant protein. The chiA enzyme was purified using His-tag affinity chromatography and showed optimal activity at 40 °C and pH 5. The purified chiA enzyme exhibited strong insecticidal activity against Myzus persicae, with an lethal dose₅₀ of 15.8 ppm. The comparative genomic analysis using MUMMER4 and MAUVE, identified horizontal gene transfer (HGT) events and genomic rearrangements within reference strain and our strain GBS19. The recombinant chiA enzyme exhibited 98.4% similarity with reference chiA sequences, highlighting its evolutionary conservation. Molecular docking studies confirmed a binding affinity of - 5.74 kcal/mol between the enzyme and chitin monomers, supported by interaction studies with modeled chitin layer. In addition, we have also predicted the most variable mutations required for enzyme stability and enzymatic activity enhancement in cloned amino acid sequence using protein AI tool, which will also guide us further studies linked to site-directed mutagenesis. This study demonstrates the potential of S. marcescens chitinase as an effective biocontrol agent against Myzus persicae. It underscores the importance of recombinant DNA technology in sustainable agriculture and sheds light on the evolutionary adaptation of chitinase genes through HGT and mutational events.