The phylogeny of bacteria belonging to the genus Nitrobacter was inves
tigated by sequencing the whole 16S rRNA gene. The average level of si
milarity for the three Nitrobacter strains examined was high (99.2%),
and the similarity level between Nitrobacter winogradskyi and Nitrobac
ter sp. strain LL, which represent two different genomic species, was
even higher (''.6%). When all of the Nitrobacter strains and their phy
logenetic neighbors Bradyrhizobium and Rhodopseudomonas species were c
onsidered, the average similarity level was 98.1%. When complete seque
nces were used, Nitrobacter hamburgensis clustered with the two other
Nitrobacter strains, while this was not the case when partial sequence
s were used. The two Rhodopseudomonas palustris strains examined exhib
ited a low similarity level (97.6%) and were not clustered.