POLYPHASIC TAXONOMIC STUDY OF THE EMENDED GENUS COMAMONAS - RELATIONSHIP TO AQUASPIRILLUM-AQUATICUM, FALSEN,E. GROUP-10, AND OTHER CLINICAL ISOLATES

We used DNA-rRNA hybridization, DNA base composition, polyacrylamide gel electrophoresis of whole-cell proteins, DNA-DNA hybridization, numerical analysis of phenotypic features, and immunotyping to study the taxonomy of the genus Comamonas. The relationships of this genus to Aquaspirillum aquaticum and a group of clinical isolates (E. Falsen group 10 [EF 10] were studied. Our DNA and rRNA hybridization results indicate that the genus Comamonas consists of at least the following five genotypic groups: (i) Comamonas acidovorans, (ii) Comamonas testosteroni, (iii) Comamonas terrigena, (iv) A. aquaticum and a number of EF 10 strains, and (v) other EF 10 strains, several unnamed clinical isolates, and some misnamed strains of Pseudomonas alcaligenes and Pseudomonas pseudoalcaligenes subsp. pseudoalcaligenes. The existence of these five groups was confirmed by the results of immunotyping and protein gel electrophoresis. A numerical analysis of morphological, auxanographic, and biochemical data for the same organisms revealed the existence of three large phena. Two of these phena (C. acidovorans and C. testosteroni) correspond to two of the genotypic groups. The third phenon contains strains belonging to the other three genotypic groups, including most EF 10 strains and the type strains of C. terrigena and A. aquaticum. The strains belonging to the third phenon were all incorporated into C. terrigena, and we propose that the use of the name Aquaspirillum aquaticum should be discontinued. Emended descriptions of the genus Comamonas and C. terrigena are presented.