Diversity of Antimicrobial Peptide Genes in Bacillus from the Andaman and Nicobar Islands: Untapped Island Microbial Diversity for Disease Management in Crop Plants

Taxonomic and functional characterization of a total of 90 bacterial isolates representing bulk and rhizosphere soils of diverse niches of Andaman and Nicobar Islands, India were carried out. Twelve bacterial isolates were found promising for the biological suppression of agriculturally important fungal and bacterial plant pathogens such as Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, and Colletotrichum gloeosporioides. The 16S rRNA gene sequence analysis revealed their identity as belonging to Bacillus subtilis, Bacillus amyloliquefaciens, and Lysinibacillus sphaericus. The isolates were positive for plant growth promotion (PGP) traits including siderophore production, and nutrient solubilization especially phosphorous, zinc, and potassium. Interestingly, the PCR test confirmed the presence of 62 antimicrobial peptides (AMP) biosynthesis genes specific to the genus Bacillus. Whilst all tested species of Bacillus harboured the bacD biosynthesis gene, the B. subtilis (Ba_Abi), and B. amyloliquefaciens (Ba_Abi) harboured the maximum AMP biosynthesis genes analysed in the study. Upon in planta evaluation, the biocontrol potential of the bacterial isolates against leaf spot disease of chilli was observed. The study culminated in the isolation and identification of diverse Bacillus species for exploitation as bioinoculants for plant health management programmes.

Automated summary

Taxonomic and functional characterization of bacterial isolates from Andaman and Nicobar Islands revealed the potential of 12 isolates for biological suppression of plant pathogens. These isolates were identified as Bacillus subtilis, Bacillus amyloliquefaciens, and Lysinibacillus sphaericus and showed plant growth promotion traits. PCR test confirmed the presence of antimicrobial peptides biosynthesis genes specific to Bacillus genus. In planta evaluation demonstrated the biocontrol potential of these isolates against chilli leaf spot disease. The study highlights the diversity of Bacillus species for bioinoculants in plant health management programs.