Comparative genome analysis and mining of secondary metabolites of Paenibacillus polymyxa

Paenibacillus polymyxa is a well-known Gram-positive biocontrol bacterium. It has been reported that many P. polymyxa strains can inhibit bacteria, fungi and other plant pathogens. Paenibacillus polymyxa employs a variety of mechanisms to promote plant growth, so it is necessary to understand the biocontrol ability of bacteria at the genome level. In the present study, thanks to the widespread availability of Paenibacillus genome data and the development of bioinformatics tools, we were able to analyze and mine the genomes of 43 P. polymyxa strains. The strain NCTC4744 was determined not to be P. polymyxa according to digital DNA-DNA hybridization and average nucleotide identity. By analysis of the pan-genome and the core genome, we found that the pan-genome of P. polymyxa was open and that there were 3,192 core genes. In a gene cluster analysis of secondary metabolites, 797 secondary metabolite gene clusters were found, of which 343 are not similar to known clusters and are expected to reveal a large number of new secondary metabolites. We also analyzed the plant growth-promoting genes that were mined and found, surpisingly, that these genes are highly conserved. The results of the present study not only reveal a large number of unknown potential secondary metabolite gene clusters in P. polymyxa, but also suggest that plant growth promotion characteristics are evolutionary adaptations of P. polymyxa to plant-related habitats.