Microvirga lupini sp nov., Microvirga lotononidis sp nov and Microvirga zambiensis sp nov are alphaproteobacterial root-nodule bacteria that specifically nodulate and fix nitrogen with geographically and taxonomically separate legume hosts

Strains of Gram-negative, rod-shaped, non-spore-forming bacteria were isolated from nitrogen-fixing nodules of the native legumes Listia angolensis (from Zambia) and Lupinus texensis (from Texas, USA). Phylogenetic analysis of the 16S rRNA gene showed that the novel strains belong to the genus Microvirga, with >= 96.1 % sequence similarity with type strains of this genus. The closest relative of the representative strains Lut6(T) and WSM3557(T) was Microvirga flocculans TFBT, with 97.6-98.0% similarity, while WSM3693(T) was most closely related to Microvirga aerilata 5420S-16(T), with 98.8 % similarity. Analysis of the concatenated sequences of four housekeeping gene loci (dnaK, gyrB, recA and rpoB) and cellular fatty acid profiles confirmed the placement of Lut6(T), WSM3557(T) and WSM3693(T) within the genus Micro virga. DNA-DNA relatedness values, and physiological and biochemical tests allowed genotypic and phenotypic differentiation of Lut6(T), W5M3557(T) and WSM3693(T) from each other and from other Micro virga species with validly published names. The nodA sequence of Lut6T was placed in a clade that contained strains of Rhizobium, Mesorhizobium and Sinorhizobium, while the 100% identical nodA sequences of WSM3557(T) and WSM3693(T) clustered with Bradyrhizobium, Burkholderia and Methylobacterium strains. Concatenated sequences for nifD and nifH show that the sequences of Lut6(T), W5M3557(T) and W5M3693(T) were most closely related to that of Rhizobium etli CFN42(T) nifDH. On the basis of genotypic, phenotypic and DNA relatedness data, three novel species of Micro virga are proposed: Micro virga lupini sp. nov. (type strain Lut6(T) = LMG 26460(T) = HAMBI 3236(T)), Micro virga lotononidis sp. nov. (type strain W5M3557(T) = LMG 26455(T) = HAMBI 3237(T)) and Micro virga zambiensis sp. nov. (type strain WSM3693(T) = LMG 26454(T) = HAMBI 3238(T)).