CHARACTERIZATION OF TROPICAL TREE RHIZOBIA AND DESCRIPTION OF MESORHIZOBIUM-PLURIFARIUM SP. NOV

A collection of strains isolated from root nodules of Acacia species i n Senegal was analysed previously by electrophoresis of total cell pro tein, auxanographic tests, rRNA-DNA hybridization, 16S rRNA gene seque ncing, DNA base composition and DNA-DNA hybridization [de Lajudie, P., Willems, A., Pot, B. & 7 other authors (1994). Int I Syst Bacteriol 4 4, 715-733]. Strains from Acacia were shown to belong to two groups, S inorhizobium terangae, and a so-called gel electrophoretic cluster U, which also included some reference strains from Brazil. Further taxono mic characterization of this group using the same techniques plus repe titive extragenic palindromic-PCR and nodulation tests is presented in this paper. Reference strains from Sudan and a number of new rhizobia isolated from nodules of Acacia senegal, Acacia tortilis subsp. raddi ana and Prosopis juliflora in Senegal were included. As a result of th is polyphasic approach, the creation of a new species, Mesorhizobium p lurifarium, is proposed for a genotypically and phenotypically distinc t group corresponding to the former cluster U and containing strains i solated from Acacia, Leucaena, Prosopis and Chamaecrista in West Afric a (Senegal), East Africa (Sudan) and South America (Brazil). The type strain of Mesorhizobium plurifarium ORS 1032 has been deposited in the LMG collection as LMC 11892.