Retracing the evolution of Pneumocystis species, with a focus on the human pathogen Pneumocystis jirovecii

• Published in: Microbiology and molecular biology reviews 2024-06, Vol.88 (2), p.e0020222
• Main Authors: Cissé, Ousmane H, Ma, Liang, Kovacs, Joseph A
• Format: Article
• Language: English
• Subjects: Animals; Biological Evolution; Cell walls; Chromosome rearrangements; Cretaceous; Evolution; Evolution, Molecular; Evolutionary genetics; Fungi; Gene flow; Genome, Fungal - genetics; Glycoproteins; Host Specificity; Humans; Immune system; Mammals; Mammals - microbiology; Mycology; Nutrients; Phylogeny; Pneumocystis - classification; Pneumocystis - genetics; Pneumocystis carinii - classification; Pneumocystis carinii - genetics; Pneumocystis carinii - pathogenicity; Pneumocystis Infections - microbiology; Pneumocystis jirovecii; Pneumonia, Pneumocystis - microbiology; Review; Sibling species; Special Series: Fungi’s Most Wanted; Speciation
• ISSN: 1092-2172; 1098-5557; 1098-5557
• DOI: 10.1128/mmbr.00202-22

SUMMARYEvery human being is presumed to be infected by the fungus at least once in his or her lifetime. This fungus belongs to a large group of species that appear to exclusively infect mammals, with being the only one known to cause disease in humans. The mystery of origin and speciation is just beginning to unravel. Here, we provide a review of the major steps of evolution. The genus likely originated from soil or plant-associated organisms during the period of Cretaceous ~165 million years ago and successfully shifted to mammals. The transition coincided with a substantial loss of genes, many of which are related to the synthesis of nutrients that can be scavenged from hosts or cell wall components that could be targeted by the mammalian immune system. Following the transition, the genus cospeciated with mammals. Each species specialized at infecting its own host. Host specialization is presumably built at least partially upon surface glycoproteins, whose protogene was acquired prior to the genus formation. appeared at ~65 million years ago, overlapping with the emergence of the first primates. and its sister species , which infects macaques nowadays, may have had overlapping host ranges in the distant past. Clues from molecular clocks suggest that did not cospeciate with humans. Molecular evidence suggests that speciation involved chromosomal rearrangements and the mounting of genetic barriers that inhibit gene flow among species.