Comparative Genomics of Pneumocystis carinii with Other Protists: Implications for Life Style

Three protistan genomes were analyzed for differential genetic traits that may be associated with biological adaptations to their unique life styles. The microsporidian, Encephalitozoon cuniculi, an obligate intracellular parasite; the ascomycetes, Pneumocystis carinii, considered an opportunistic p...

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Bibliographic Details
Published in:The Journal of eukaryotic microbiology 2004-01, Vol.51 (1), p.30-37
Main Author: CUSHION, MELANIE T.
Format: Article
Language:English
Subjects:
Animals
DNA, Fungal - genetics
DNA, Ribosomal - genetics
Free-living
Genomics
Humans
model organism
obligate intracellular parasite
opportunistic pathogen
Phylogeny
Pneumocystis carinii - classification
Pneumocystis carinii - genetics
Pneumocystis carinii - metabolism
Pneumocystis Infections - physiopathology
Pneumocystis Infections - veterinary
Saccharomyces cerevisiae - classification
Saccharomyces cerevisiae - genetics
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Summary:Three protistan genomes were analyzed for differential genetic traits that may be associated with biological adaptations to their unique life styles. The microsporidian, Encephalitozoon cuniculi, an obligate intracellular parasite; the ascomycetes, Pneumocystis carinii, considered an opportunistic pathogen; and Saccharomyces cerevisiae, a model organism exhibiting a free-living life style, were used in comparisons of genomic architecture, reproductive strategies, and metabolic capacity predicted by the presence of signature genes. Genome size, gene number, and metabolic function decreased as the organisms became more dependent on their hosts. In contrast, gene density and the percentage of genes dedicated to cell growth and division were substantially increased in the genome of E. cuniculi. The obligate life style was associated with reductions in gene number, genome size, and reduced metabolic capacity while the free-living life style was coincident with gene duplications and duplication of large portions of the genome. The genomic characteristics and metabolic capacity of P. carinii were usually intermediate between those of the other two protistan genomes, but unique characteristics such as the presence of a single rDNA locus may indicate that these organisms could be in the process of becoming more host dependent.
ISSN:1066-5234
1550-7408
DOI:10.1111/j.1550-7408.2004.tb00158.x