Molecular Characterization and Antibacterial Activities of Photorhabdus and Xenorhabdus from Mizoram, North-East India

Photorhabdus and Xenorhabdus are the bacterial symbionts of insect pathogenic nematodes, Heterorhabditis and Steinernema, respectively. This study aims to characterize the bacterial symbionts from Mizoram, North-east India and to evaluate their antibacterial potential. The bacterial isolates were characterized using recA and gyrB gene regions. The ethyl acetate extract of bacterial isolates was tested against pathogenic bacterial strains, viz. Escherichia coli (ATCC 10536), Klebsiella pneumoniae (ATCC 10031), Pseudomonas aeruginosa (ATCC 10145), and Bacillus subtilis (ATCC 11774) using disk diffusion method. Analysis of recA and gyrB genes revealed that the Photorhabdus isolates were P. hindustanensis, and P. namnaonensis. This study constitutes the first documentation of P. namnaonensis from India. The two isolated Xenorhabdus belong to X. vietnamensis and X. stockiae. The ethyl acetate extracts of the studied bacteria suppressed the development of all the microorganisms tested. Based on MIC and MBC values, the highest activity was exhibited by TS (P. hindustanensis) and TD (P. namnaonensis) isolates against P. aeruginosa and K. pneumoniae respectively. The lowest inhibitory activity was observed on both Xenorhabdus isolates (RF and PTS) against B. subtilis. This study focuses on the existence and identification of symbiotic bacteria from Mizoram, an Indo-Burma biodiversity hotspot region, and details their activity against different pathogenic bacteria. Since these metabolites could be potent antibiotics, further research is required to better understand the genetic information, chemical composition, and method of action against other microorganisms.