PHYLOGENETIC-RELATIONSHIPS AMONG THE CHROMATIACEAE, THEIR TAXONOMIC RECLASSIFICATION AND DESCRIPTION OF THE NEW GENERA ALLOCHROMATIUM, HALOCHROMATIUM, ISOCHROMATIUM, MARICHROMATIUM, THIOCOCCUS, THIOHALOCAPSA AND THERMOCHROMATIUM

Sequences of the 16S rDNA from ail available type strains of Chromatiu m species have been determined and were compared to those of other Chr omatiaceae, a few selected Ectothiorhodospiraceae and Escherichia coil . The clear separation of Ectothiorhodospiraceae and Chromatiaceae is confirmed. Most significantly the sequence comparison revealed a genet ic divergence between Chromatium species originated from freshwater so urces and those of truly marine and halophilic nature. Major phylogene tic branches of the Chromatiaceae contain (i) marine and halophilic sp ecies, (ii) freshwater Chromatium species together with Thiocystis spe cies and (iii) species of the genera Thiocapsa and Amoebobacter as rec ently reclassified [Guyoneaud. R. & 6 other authors (1998). Int J Syst Bacteriol 48, 957-964], namely Thiocapsa roseopersicina, Thiocapsa pe ndens (formerly Amoebobacter pendens), Thiocapsa roses (formerly Amoeb obacter roseus), Amoebobacter purpureus and Thiolamprovum pedioforme ( formerly Amoebobacter pedioformis). The genetic relationships between the species and groups are not in congruence with the current classifi cation of the Chromatiaceae and a reclassification is proposed on the basis of 16S rDNA sequence similarity supported by selected phenotypic properties. The proposed changes include the transfers of Chromatium minus and Chromatium violascens to Thiocystis minor comb. nov. and Thi ocystis violascens comb. nov., of Chromatium vinosum, Chromatium minut issimum and Chromatium warmingii to the new genus Allochromatium. as A llochromatium vinosum comb. nov., Allochromatium minutissimum comb. no v., and Allochromatium warmingii comb. nov., of Chromatium tepidum to the new genus Thermochromatium as Thermochromatium tepidum comb. nov., of Chromatium salexigens and Chromatium glycolicum to the new genus H alochromatium as Halochromatium salexigens comb. nov. and Halochromati um glycolicum comb. nov., of Chromatium gracile and Chromatium purpura tum to the new genus as Marichromatium gracile comb. nov. and Marichro matium purpuratum comb, nov., of Thiocapsa pfennigii to Thiococcus pfe nnigii gen. nom. rev., of Thiocapsa halophila to the new genus Thiohal ocapsa as Thiohalocapsa halophila comb. nov., and of Chromatium buderi to the new genus Isochromatium as Isochromatium buderi comb. nov.