Nodule morphology, symbiotic specificity and association with unusual rhizobia are distinguishing features of the genus Listia within the Southern African crotalarioid clade Lotononis s.l.

Background And Aims: The legume clade Lotononis sensu lato (s.l.; tribe Crotalarieae) comprises three genera: Listia, Leobordea and Lotononis sensu stricto (s.

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.

Root nodule bacteria isolated from South African Lotononis bainesii, L. listii and L. solitudinis are species of Methylobacterium that are unable to utilize methanol.

The South African legumes Lotononis bainesii, L. listii and L. solitudinis are specifically nodulated by highly effective, pink-pigmented bacteria that are most closely related to Methylobacterium nodulans on the basis of 16S rRNA gene homology.