Re-evaluation of the nodulation capacity of DSM 18106 indicates that this strain is not capable of inducing root nodule formation on (pea).

Rhizobia are soil-dwelling proteobacteria that can enter into symbiotic nitrogen-fixing relationships with compatible leguminous plants. Taxonomically, rhizobia are divided into alpha-rhizobia, which belong to the class , and beta-rhizobia, which belong to the class . To date, all bona fide alpha-rhizobia belong to the order . However, a recent study suggested that DSM 18106 is also a rhizobium and is capable of nodulating pea plants (), which would expand the known taxonomic distribution of alpha-rhizobia to include the order . Here, we attempted to replicate the results of that previous study. Resequencing and computational analysis of the genome of DSM 18106 failed to identify genes encoding proteins involved in legume nodulation or nitrogen fixation. In addition, experimental plant assays indicated that DSM 18106 is unable to nodulate the two cultivars of pea tested in our study, unlike the rhizobium 3841. Taken together, and in contrast to the previous study, these results suggest that DSM 18106 is not capable of inducing root nodule formation on pea, meaning that the taxonomic distribution of all known alpha-rhizobia remains limited to the class .