The inclusion of this bacterium into the "Pseudomonas" genus was confirmed by DNA-DNA hybridization and similarity comparisons of the rRNA sequences. Four "rrn" operons and an origin of replication site have been identified in "P. stutzeri". Strains of "P. stutzeri" are divided into separate genomic groups called genomovars. The genomovar concept was used for "P. stutzeri" to distinguish genotypically similar strains. Two strains of "P. stutzeri" can be classified in a single genomovar if DNA-DNA similarity is at least 70% similar. Seven genomovars have been characterized and their genome sizes range from 3.75–4.64 Mbp. These differences in genomovar genomes are believed to have been caused by chromosomal rearrangements during its evolution.