Description of Comamonas aquatica comb. nov. and Comamonas kerstersii sp. nov. for two subgroups of Comamonas terrigena and emended description of Comamonas terrigena.

Three clusters of isolates have previously been defined within the species Comamonas terrigena, on the basis of DNA-rRNA and DNA-DNA hybridization data, and of protein electrophoretic patterns and immunotyping. More detailed characterization in the current study shows that representatives of these three groups can also be differentiated phenotypically from each other. Strains of C. terrigena sensu stricto (C. terrigena DNA group 1) are pyrrolidone aminopeptidase-positive, do not grow at 40 degrees C, are L-alanine-positive and are always negative for 4-hydroxybenzoate. Strains of C. terrigena DNA groups 2 and 3 are pyrrolidone aminopeptidase-negative; the former is the only group that is tyrosine-negative, and only the latter can grow at 42 degrees C (with an optimal growth temperature of 40 degrees C). These findings are corroborated by differences in 16S rDNA sequence and tRNA intergenic spacer lengths. Therefore, it is proposed to rename C. terrigena DNA group 2 [containing former Aquaspirillum aquaticum and E. Falsen (EF) group 10 strains] as Comamonas aquatica sp. nov., and C. terrigena DNA group 3 (containing former EF group 10 strains) as Comamonas kerstersii sp. nov.