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

摘要

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 % or greater sequence similarity with type strains of this genus. The closest relative of the representative strains Lut6T and WSM3557T was M. flocculans TFBT, with 97.6-98.0 % similarity, while WSM3693T was most closely related to M. aerilata 5420S-16T, with 98.8 % similarity. Analysis of the concatenated sequences of four housekeeping gene loci (dnaK, gyrB, recA, rpoB) and cellular fatty acid profiles confirmed the placement of Lut6T, WSM3557T and WSM3693T within Microvirga. DNA:DNA relatedness values and physiological and biochemical tests allowed genotypic and phenotypic differentiation of Lut6T, WSM3557T and WSM3693T from each other and from other validly published Microvirga species. 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 WSM3557T and WSM3693T clustered with Bradyrhizobium, Burkholderia and Methylobacterium strains. Concatenated sequences for nifD and nifH show that Lut6T, WSM3557T and WSM3693T were most closely related to Rhizobium etli CFN42T nifDH. On the basis of genotypic, phenotypic and DNA relatedness data, three novel species of Microvirga are proposed: Microvirga lupini (Lut6T = LMG26460T, = HAMBI 3236) Microvirga lotononidis (WSM3557T = LMG26455T, = HAMBI 3237) and Microvirga zambiensis (WSM3693T = LMG26454T, = HAMBI 3238).