Crown gall
tumors, collected from branches of 1-year-old weeping fig (Ficus benjamina L.) trees, yielded both tumorigenic and nonpathogenic agrobacteria. On the basis of classical diagnostic tests, the nonpathogenic strains were identified as Agrobacterium tumefaciens, whereas the tumorigenic strains could not be assigned to any of the known terrestrial Agrobacterium spp. The tumorigenic strains also differed from other members of the genus by producing more
acid from
mannitol. According to cluster analysis of
carbon substrate oxidation (GN Microplate; Biolog, Inc.) and
fatty acid content, the tumorigenic fig strains were distinct from strains of A. tumefaciens, Agrobacterium rhizogenes, Agrobacterium vitis, and Agrobacterium rubi. Furthermore, they had unusual opine metabolism, inducing
tumors that synthesized
nopaline and three recently discovered opines:
chrysopine (d-
lactone of N-1-deoxy-D-fructosyl-
L-glutamine, and N-1-deoxy-D-fructosyl-
L-glutamine, and N-1-deoxy-D-fructosyl-5-oxo-
L-proline. The nonpathogenic A. tumefaciens strains present in the same
tumors were unable to degrade any of the opines tested. The phylogenetic position of the tumorigenic fig strain AF3.10 was inferred from comparing its rrs (i.e.,
16S rRNA gene) sequence with those from the type strains of Agrobacterium and Rhizobium species. The analysis showed that strain AF3.10 clustered with A. tumefaciens and A. rubi but not with A. vitis and was far removed from A. rhizogenes. However, the sequence was significantly different from those of A. tumefaciens and A. rubi to suggest that the tumorigenic fig strain may be a new Agrobacterium species that is as different from A. tumefaciens and A. rubi as these two species are from one another.