"Revealing the genetic arsenal of Bacillus firmus TNAU1: Unleashing nematicidal and plant growth promotion traits"

Abstract

Bacillus firmus is a promising nematicidal bacterium that also confers plant growth promotion, nutrient acquisition and antimicrobial activities. In the present study, attempts were made for whole genome sequencing of B. firmus TNAU1 isolated from the rhizosphere region of cucumber. The results confirmed that the isolate was B. firmus which contained a single circular genome of 5,370,919 bp (5.3 Mb) in length with an average GC content of 41.16 %. Annotation was performed using PATRIC tool to explore the subsystem analysis, specialty genes, Enzyme Commission (EC) numbers, Gene Ontology (GO) mappings, KEGG pathways of B. firmus TNAU1. A total of 5804 coding sequence (CDS) genes that encode proteins were predicted based on the KEGG and clusters of orthologous groups (COGs) database. Comparative genomic analysis was performed to discover the unique features and their relationship with other available B. firmus strains. Blastp analysis revealed that TNAU 1 genome assemblies had 26 homologs corresponding to nematode-virulent proteases and various genes responsible for plant growth promotion which includes indole acetic acid (IAA) production, nitrate transport, phosphorus and potassium solubilization. Four secondary metabolite biosynthetic clusters encoding antibiotics and siderophore production were confirmed through comparative genomics. B. firmus TNAU1 was evaluated for its antagonistic activity against root-knot nematode Meloidogyne incognita of tomato. The results exhibited that B. firmus inhibited the egg hatching and mortality of juveniles by 96% over control under in vitro conditions and greenhouse experiments confirmed that the TNAU1 strain not only had the potential to suppress the soil and root population of M. incognita (70% reduction over control), but also triggered the plant growth parameters of tomato.