{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T06:15:51Z","timestamp":1790144151839,"version":"4.0.1"},"reference-count":48,"publisher":"American Society for Microbiology","issue":"1","license":[{"start":{"date-parts":[[2003,1,1]],"date-time":"2003-01-01T00:00:00Z","timestamp":1041379200000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Infect Immun"],"published-print":{"date-parts":[[2003,1]]},"abstract":"<jats:title>ABSTRACT<\/jats:title><jats:p><jats:italic>Pneumocystis carinii<\/jats:italic>expresses a surface glycoprotein called MSG. Different isoforms of MSG are encoded by a gene family spread over at least 15 telomeric sites. Only one locus, called UCS, supports the production of MSG mRNA. Previous studies showed that<jats:italic>P. carinii<\/jats:italic>populations from individual rats exhibited high degrees of diversity with respect to the MSG genes attached to the UCS locus. This diversity could have been generated primarily in the rats studied. Alternatively, the rats may have been infected by<jats:italic>P. carinii<\/jats:italic>organisms that were already different at the UCS locus. To investigate this issue, we examined the UCS locus in<jats:italic>P. carinii<\/jats:italic>from rats that had been exposed to few of the microbes at a specified time, which produced a bottleneck in the microbial population. Some of the rats with bottlenecks produced<jats:italic>P. carinii<\/jats:italic>populations in which a single MSG sequence resided at the UCS locus in 80 to 90% of the organisms, showing that<jats:italic>P. carinii<\/jats:italic>can proliferate within a rat without generating the very high levels of UCS diversity previously seen. From the degree of diversity observed in the bottlenecked populations, the maximum rate of switching appeared to be 0.01 event per generation. These data also suggest that the infectious dose is as low as one organism, that rats that share a cage readily infect each other, and that the doubling time of<jats:italic>P. carinii<\/jats:italic>in vivo is \u223c3 days. In addition, we found that inoculation with 10<jats:sup>7<\/jats:sup><jats:italic>P. carinii<\/jats:italic>organisms from a population highly heterogeneous at the UCS locus reproduced this heterogeneity. By contrast, shifts in population structure occurred in rats given 10<jats:sup>4<\/jats:sup><jats:italic>P. carinii<\/jats:italic>organisms, suggesting that a small fraction of these proliferated.<\/jats:p>","DOI":"10.1128\/iai.71.1.47-60.2003","type":"journal-article","created":{"date-parts":[[2002,12,20]],"date-time":"2002-12-20T23:07:23Z","timestamp":1040425643000},"page":"47-60","update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":24,"title":["Diversity at the Locus Associated with Transcription of a Variable Surface Antigen of<i>Pneumocystis carinii<\/i>as an Index of Population Structure and Dynamics in Infected Rats"],"prefix":"10.1128","volume":"71","author":[{"given":"Scott P.","family":"Keely","sequence":"first","affiliation":[{"name":"Department of Molecular Genetics, Biochemistry and Microbiology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Melanie T.","family":"Cushion","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0524"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"James R.","family":"Stringer","sequence":"additional","affiliation":[{"name":"Department of Molecular Genetics, Biochemistry and Microbiology"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","reference":[{"key":"e_1_3_2_2_2","doi-asserted-by":"crossref","first-page":"542","DOI":"10.1183\/09031936.98.11030542","volume":"11","year":"1998","unstructured":"Aliouat, E. 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