title: Ribosomal RNA sequence shows Pneumocystis carinii to be a member of the fungi.
abstract: Pneumocystis carinii pneumonia is the most common opportunistic infection in AIDS, and accounts for significant morbidity and mortality in these and other immunocompromised patients. P. carinii is a eukaryotic microorganism of uncertain taxonomy that can infect numerous mammalian hosts. Developing from a small, unicellular 'trophozoite' into a 'cyst' containing eight 'sporozoites', its life cycle superficially resembles those seen both in the Protozoa and Fungi. Morphological and ultrastructural observations have lead some investigators to conclude that the organism is a protozoan, while others have felt that it more closely resembles a fungus. Phylogenetic relationships can be inferred from comparisons of macromolecular sequences. Small subunit ribosomal RNAs (16S-like rRNAs) are well-suited for this purpose because they have the same function in all organisms and contain sufficient information to estimate both close and distant evolutionary relationships. Phylogenetic frameworks based upon such comparisons reveal that the plant, animal and fungal lineages are distinct from the diverse spectrum of protozoan lineages. In this letter, phylogenetic analysis of Pneumocystis 16S-like rRNA demonstrates it to be a member of the Fungi.
authors.affiliation: Hormone Research Institute, University of California, San Francisco 94143-0534.
authors.forename: J C
authors.initials: JC
authors.lastname: Edman
authors.forename: J A
authors.initials: JA
authors.lastname: Kovacs
authors.forename: H
authors.initials: H
authors.lastname: Masur
authors.forename: D V
authors.initials: DV
authors.lastname: Santi
authors.forename: H J
authors.initials: HJ
authors.lastname: Elwood
authors.forename: M L
authors.initials: ML
authors.lastname: Sogin
mesh_terms: D000818:Animals; D001483:Base Sequence; D001710:Biotin / Q000031:analogs & derivatives; D003856:Deoxyuracil Nucleotides / Q000378:metabolism; D056890:Eukaryota / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000235:genetics; D009693:Nucleic Acid Hybridization; D010802:Phylogeny; D011010:Pneumocystis / Q000145:classification / Q000235:genetics*; D012331:RNA, Fungal / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000235:genetics
chemical_list: D003856:Deoxyuracil Nucleotides; D012331:RNA, Fungal; D012335:RNA, Ribosomal; D012336:RNA, Ribosomal, 16S; C027078:deoxyuridine triphosphate; D001710:Biotin