Characterization of two novel biovar of Agrobacterium tumefaciens isolated from root nodules of Vicia faba

A total of eight strains of bacteria were isolated from the root nodule of Vicia faba on the selective media of Rhizobium. Two of these strains produced phenotypically distinct mucoid colonies (one slow growing and the other fast growing) and were examined using a polyphasic approach for taxonomic identification. The two strains (MTCC 7405 and MTCC 7406) turned out to be new strains of biovar 1 Agrobacterium rather than Rhizobium, as they showed growth on alkaline medium as well as on 2% NaCl and neither catabolized lactose as the carbon source nor oxidized Tween-80. The distinctness between the two strains was marked with respect to their growth on dextrose and the production of lysine dihydrolase, ornithine decarboxylase and DNA G + C content. 16S rDNA sequencing and their comparison with the 16S rDNA sequences of previously described agrobacteria as well as rhizobia strains confirmed the novelty of the two strains. Both of the strains clustered with strains of Agrobacterium tumefaciens in the 16S rDNA-based phylogenetic tree. The phenotypic and biochemical properties of the two strains differed from those of the recognized biovar of A. tumefaciens. It is proposed that the strains MTCC 7405 and MTCC 7406 be classified as novel biovar of the species A. tumefaciens (Type strains MTCC 7405 = DQ383275 and MTCC 7406 = DQ383276).