Paenibacillus agilis sp. nov., Paenibacillus cremeus sp. nov. and Paenibacillus terricola sp. nov., isolated from rhizosphere soils.

Abstract

Members of the genus Paenibacillus are well known for their metabolic versatility and great application potential in plant growth promotion. Three novel bacterial strains, designated N4T, JC52T and PR3T, were isolated from rhizosphere soils and characterized by using a polyphasic taxonomic approach. The 16S rRNA gene sequence phylogenetic and phylogenomic analysis revealed that the three strains belonged to the genus Paenibacillus and formed three independent branches distinct from all reference strains. The results of DNA-DNA hybridization (DDH) and average nucleotide identity (ANI) analyses between the three strains and their relatives further demonstrated that the three strains represented different novel genospecies. Strain N4T exhibited the highest similarity, ANI and digital DDH values with Paenibacillus assamensis DSM 18201T (99.0/87.5/33.9 %) and Paenibacillus insulae DS80T (97.2/-/18.2±1.2 %). Values for JC52T with Paenibacillus validus NBRC 15382T were 96.9, 73.3 and 19.6 %, and with Paenibacillus rigui JCM 16352T were 96.1, 72.1 and 19.3 %. Values for PR3T with Paenibacillus ginsengiterrae DCY89T were 98.2, - and 31.8±1.5 %, with Paenibacillus cellulosilyticus ASM318225v1T were 97.8, 83.3 and 26.7 %, and with Paenibacillus kobensis NBRC 15729T were 97.6, 75.7 and 20.4 %. Cells of the three novel bacterial strains were Gram-positive, spore-forming, motile and rod-shaped. The novel species contained anteiso-C15 : 0 and MK-7 as the predominant fatty acid and menaquinone, respectively. The novel strains have numerous similar known clusters of non-ribosomal peptide synthetases, siderophores, lanthipeptide, lassopeptide-like bacillibactin, paeninodin and polyketide-like chejuenolide A/B lankacidin C. Based on the distinct morphological, physiological, chemotaxonomic and phylogenetic differences from their closest phylogenetic neighbours, we propose that strains N4T, JC52T and PR3T represent novel species of the genus Paenibacillus, with the names Paenibacillus agilis sp. nov. (=KACC 19717T=JCM 32775T), Paenibacillus cremeus sp. nov. (=KACC 21221T=NBRC 113867T) and Paenibacillus terricola sp. nov. (=KACC 21455T=NBRC 114385T), respectively.