Mycoplasma cavipharyngis and Mycoplasma fastidiosum, the closest relativesto Eperythrozoon spp. and Haemobartonella spp.

The 16S rRNA gene sequences of Mycoplasma cavipharyngis and Mycoplasma fast idiosum have been determined. Phylogenetic analysis showed that these speci es formed a new cluster within the so-called pneumoniae group of the mollic utes (class Mollicutes). This fluster will be referred to as the M. fastidi osum cluster. Interestingly, the M. fastidiosum cluster formed a sister lin eage to the haemotrophic bacteria, Eperythrozoon spp. and Haemobartonella s pp. The two latter genera, formerly classified as rickettsias, formed a sta ble phylogenetic entity in the tree as judged from branch lengths, bootstra p values and sequence signatures. Thus, the members of the M. fastidiosum c luster are the closest known relatives to the haemotrophic bacteria. Our da ta strongly support that the haemotrophic bacteria should be reclassified t o reflect their actual phylogenetic affiliation. (C) 1999 Federation of Eur opean Microbiological Societies. Published by Elsevier Science B.V. Ail rig hts reserved.