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

A bacterial strain designated SBR5(T) 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 RSA19(T) (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 SBR5(T) 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-C(15 : 0). DNA-DNA hybridization values between strain SBR5(T) and P. graminis RSA19(T), Paenibacillus odorifer TOD45(T) and Paenibacillus borealis KK19(T) were 43, 35 and 28 %, respectively. These DNA relatedness data and the results of phylogenetic and phenotypic analyses showed that strain SBR5(T) 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 SBR5(T) (=CCGB 1313(T) =CECT 7330(T)).