A re-evaluation of the taxonomy of Paracoccus denitrificans and a proposal for the combination Paracoccus pantotrophus comb. nov

1 Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA 2 Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK 3 DSMZ --- Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Mascheroder Weg 1b, D-38124 Braunschweig, Germany 4 Department of Ecological Engineering, Toyohashi University of Technology, Tenpaku-cho, Toyohashi 441, Japan 5 Department of Environmental and Natural Resources Science, Tokyo University of Agriculture and Technology, Fuchu 183, Japan 6 Microbiology Research Group, Division of Life Sciences, King's College London, Campden Hill Road, London W8 7AH, UK Author for correspondence: Donovan P. Kelly. Tel: +44 1203 572907. Fax: +44 1203 523701. e-mail: mmza{at}dna.bio.warwick.ac.uk ABSTRACT Comparison of both 16S rRNA coding sequences and DNA-DNA hybridization of ten strains of -subclass of Proteobacteria currently classified as strains of Paracoccus denitrificans has shown that they fall into two groups which are distinct from each other at the species level. Comparison with published data on the cytochrome c profiles and other 16S rRNA coding sequences in the literature has confirmed these observations and enabled several other strains also to be assigned to these two groups. Group A comprises strains ATCC 17741 T (the type strain of P. denitrificans ), LMD 22.21 T , DSM 413 T , ATCC 19367, ATCC 13543, DSM 1404, DSM 1405, Pd 1222 (a genetic modification of DSM 413 T ) and NCIMB 8944. Group B comprises ATCC 35512 T (the original type strain of Thiosphaera pantotropha ), LMD 82.5 T , LMD 92.63, DSM 65, LMG 4218, IAM 12479, JCM 6892, DSM 11072, DSM 11073 and DSM 11104. In light of these findings, it is proposed that: (1) strains of group A are retained as P. denitrificans , with ATCC 17741 T as the type strain of the type species; and (2) all strains of group B are assigned to the new species combination Paracoccus pantotrophus comb. nov., with strain ATCC 35512 T as the type strain. Comparative 16S rRNA sequence analysis and DNA-DNA hybridization of strains of Paracoccus versutus confirm that this species is distinct from both P. denitrificans and P. pantotrophus , but that its nearest phylogenetic neighbour is P. pantotrophus . Key Words: Paracoccus denitrificans • Paracoccus pantotrophus • Thiosphaera • 16S rRNA gene sequencing • DNA-DNA hybridization The EMBL accession numbers for the 16S rRNA gene sequences reported in this paper are given in Table 1.