Pneumocystis carinii: Sequence from ribosomal RNA implies a close relationship with fungi

doi:10.1016/0014-4894(89)90130-6

Experimental Parasitology

Volume 68, Issue 4, May 1989, Pages 450-461

https://doi.org/10.1016/0014-4894(89)90130-6 Get rights and content

Abstract

Pneumocystis carinii is the etiologic agent of a lethal pneumonia which occurs in patients with the acquired immune deficiency syndrome (AIDS) and other immunocompromised hosts. The basic biochemical and genetic characteristics of P. carinii are poorly understood and its taxonomic classification as a protozoan is uncertain. To address the taxonomic question, a method was developed for the extraction of total RNA from P. carinii. Denaturing agarose gel electrophoresis showed the two ribosomal RNA species of P. carinii to be similar in size to those of other lower eukaryotes, including Saccharomyces cerevisiae. Three portions of the small ribosomal RNA of P. carinii were sequenced by reverse transcription from oligonucleotide primers. Three hundred seventy-two nucleotides of sequence were obtained. The sequence derived from P. carinii RNA contained regions that previous phylogenetic studies have shown to be highly variable among species, as well as regions that are highly conserved. Comparison of the P. carinii sequence to corresponding sequences of organisms from other taxa showed the P. carinii sequence to be more similar to sequences from the fungi (Saccharomyces cerevisiae, Neurospora crassa, Candida albicans, and Cryptococcus diffuens) than to protozoan sequences. These data suggest that P. carinii is more closely related to fungi than to protozoa.

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It was originally identified in the early 20th century with the name Pneumocystis given in recognition of the organism’s pulmonary tropism and carinii to honor Antonio Carini who had identified the organism in the lungs of sewer rats.53 While initially believed to be a protozoan, ribosomal RNA sequencing in the late 1980s revealed it to be more closely related to fungi.54,55 Interestingly, Pneumocystis displays features that are atypical of most fungi including that it is unable to be grown in vitro in fungal culture media, it responds to some antiparasitic agents, and its cell wall contains cholesterol rather than ergosterol which is a property that makes amphotericin and some other fungal agents ineffective toward it.56
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Citation Excerpt :
Based on morphologic criteria and response of the infection to treatment with the antiprotozoan drug pentamidine, it was initially thought that P carinii was a protozoan. In 1988, Edman and Stringer independently showed that the ribosomal RNA sequences of P carinii were related to those of fungus and completely unrelated to those of other parasites.15,16 All recent phylogenetic analyses place Pneumocystis within the fungal kingdom.

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Regular articlePneumocystis carinii: Sequence from ribosomal RNA implies a close relationship with fungi

Abstract

Journal of Biological Chemistry

Analytical Biochemistry

Experimental Parasitology

Trends in Biochemical Sciences

Gene

Molecular and Biochemical Parasitology

Journal of Biological Chemistry

Experimental Parasitology

Further observations on the ultrastructure of pneumocystis

Archives of Pathology

Pneumocystis carinii in the lungs of rats treated with cortisone acetate

American Journal of Pathology

The molecular evolution of genes and proteins: A tale of two serines

Science

A method for isolation of intact, translationally active ribonucleic acid

DNA

Nova tripanoaomiaza humana

Memorial Institute Oswaldo Cruz

Analysis of the developmental stages of Pneumocystis carinii, in vitro

Laboratory Investigation

Basic Methods in Molecular Biology

Comparison of the nucleotide sequence of soybean 18s rRNA with the sequence of the small subunit rRNAs

Journal of Molecular Evolution

Ribosomal RNA sequence shows Pneumocystis carinii to be a member of the fungi

Nature (London)

The small subunit ribosomal RNA gene sequences from the hypotrichous ciliates Oxytricha nova and Stylonychia pustulata

Molecular Biological Evolution

Numerical methods for inferring evolutionary trees

Quarterly Review of Biology

Construction of phylogenetic trees: A method based on mutation distances as estimated from cytochrome c sequences is of general applicability

Science

Latent pneumocystis infection of rats, relapse and chemotherapy

Laboratory Investigation

Sequence of the small subunit ribosomal RNA gene expressed in the bloodstream stages of Plasmodium berghei: Evolutional implications

Journal of Protozoology

Regular article
Pneumocystis carinii: Sequence from ribosomal RNA implies a close relationship with fungi