Genome-based reclassification of Paenibacillus jamilae Aguilera et al. 2001 as a later heterotypic synonym of Paenibacillus polymyxa (Prazmowski 1880) Ash et al. 1994

Abstract

Paenibacillus is one of the genera that has high species diversity and Paenibacillus polymyxa, the type species of the genus, is mainly isolated from plant-associated environments. Among the plant-associated species, Paenibacillus jamilae B.3(T) (=CECT 5266(T)=DSM 13815(T)=KACC 10925(T)=KCIC 13919(T)) was proposed to be a novel species according to 16S rRNA gene similarity and DNA-DNA relatedness with related species, including Paenibacillus polymyxa. Nevertheless, in the description of Paenibacillus jamilae the used strain of Paenibacillus polymyxa was not the type strain of this species. In this work we found that the type strains of both species showed 16S rRNA gene similarity of 99.6%. Therefore, in this study, we sequenced the genome of Paenibacillus jamilae KACC 10925(T) and compared it with those of the type strain of Paenibacillus polymyxa ATCC 842(T) and other phylogenetically related species. Genome relatedness value calculated by DNA-DNA hybridization between type strains of Paenibacillus polymyxa and Paenibacillus jamilae was 73.5%, which is higher than the threshold value (70%). For more objective and repeatable results of genome relatedness, we analysed an average nucleotide identity (ANI) between two strains. Our results showed that ANI value between the type strains of Paenibacillus jamilae and Paenibacillus polymyxa is 98.5%, a phylogenetic distance also higher than the threshold values (95 similar to 96%). These values were proposed by Yoon et al. (2017). In addition, their phylogenetic distance based on 92 bacterial core genes is highly close compared to other species. These mean that Paenibacillus jamilae and Paenibacillus polymyxa should be reclassified as a single species. Based on the results from genomic level comparison as well as reexamination results of physiological and chemotaxonomic features, we propose reclassification of Paenibacillus jamilae as a later heterotypic synonym of Paenibacillus polymyxa.