TAXONOMIC REARRANGEMENTS OF THE GENERA THIOCAPSA AND AMOEBOBACTER ON THE BASIS OF 16S RDNA SEQUENCE ANALYSES, AND DESCRIPTION OF THIOLAMPROVUM GEN. NOV

Complete nucleotide sequences of the 16S rDNAs were determined from Th iocapsa and Amoebobacter species, including all available type strains and some additional isolates. The distance-matrix analysis and the de ndrogram for estimating the genetic relationships revealed that the in vestigated strains were found in two major clusters within the Chromat iaceae. One cluster comprises all Amoebobacter species, Thiocapsa rose opersicina and several isolates related to Thiocapsa roseopersicina. R epresentatives of the species Amoebobacter roseus, Amoebobacter penden s and Thiocapsa roseopersicina, the so called 'Thiocapsa roseopersicin a group', are very closely related, justifying their inclusion into on e genus, Thiocapsa, for which an emended description is presented. Amo ebobacter purpureus and Amoebobacter pedioformis formed two separate l ines of descent with less than 93% (89.6-92.9%) similarity to strains of the 'Thiocapsa roseopersicina group'. Therefore, they will be consi dered as two separate genera. As a consequence, an emended description is presented for the genus Amoebobacter, with Amoebobacter purpureus as the new type species and A. pedioformis is transferred to Thiolampr ovum pedioforme gen. nov., comb. nov. Two species, Thiocapsa pfennigii and Thiocapsa halophila, which have been classified with the genus Th iocapsa because of their morphological properties, were found within a nother major cluster of the Chromatiaceae and are only distantly phylo genetically related to the first cluster with 88.4-90.6 % and 90.4-92. 2 % sequence similarity, respectively.