Paenibacillus riograndensis sp. nov., a nitrogen-fixing species isolated from the rhizosphere of Triticum aestivum

Abstract

A bacterial strain designated SBR5T was isolated from the rhizosphere of Triticum aestivum. A phylogenetic analysis based on the 16S rRNA gene sequence placed the isolate within the genus Paenibacillus, being most closely related to Paenibacillus graminis RSA19T (98.1 % similarity). The isolate was a Gram-reaction-variable, motile, facultatively anaerobic bacterium, with spores in a terminal position in cells. Starch was utilized and dihydroxyacetone and catalase were produced. Strain SBR5T displayed plant-growth-promoting rhizobacteria characteristics: the ability to fix nitrogen and to produce siderophores and indole-3-acetic acid. The DNA G+C content was 55.1 mol%. Chemotaxonomic analysis of the isolated strain revealed that MK-7 was the predominant menaquinone, while the major fatty acid was anteiso-C15 : 0. DNA–DNA hybridization values between strain SBR5T and P. graminis RSA19T, Paenibacillus odorifer TOD45T and Paenibacillus borealis KK19T were 43, 35 and 28 %, respectively. These DNA relatedness data and the results of phylogenetic and phenotypic analyses showed that strain SBR5T should be considered as the nitrogen-fixing type strain of a novel species of the genus Paenibacillus, for which the name Paenibacillus riograndensis sp. nov. is proposed. The type strain is SBR5T (=CCGB 1313T =CECT 7330T).