Tanriverdi Sultan, Widmer Giovanni
Tufts University School of Veterinary Medicine, Division of Infectious Diseases, 200 Westborough Road, North Grafton, MA 01536, USA.
Infect Genet Evol. 2006 Mar;6(2):113-22. doi: 10.1016/j.meegid.2005.02.002. Epub 2005 Mar 17.
Cryptosporidium parvum and Cryptosporidium hominis are two morphologically identical species of Apicomplexan protozoa infecting humans. Although the genomes of these species are 97% identical, their host range is strikingly different. C. parvum infects humans and animals and is primarily a zoonotic infection, whereas C. hominis is typically not detected in animals. The extent of genetic polymorphism in both species has been surveyed locally, but not on a larger geographical scale. Herein, a collection of unrelated C. parvum and C. hominis isolates was genotyped using multiple, randomly distributed micro- and minisatellites. In average, minisatellites, consisting of tandemly repeated sequence motifs of 6-24 basepair, were more polymorphic than microsatellites. When the average number of micro- and minisatellite alleles per locus was used as a measure of heterogeneity, no difference between C. parvum and C. hominis was found. However, the frequency distribution of alleles in both species was significantly different and in 6 of the 14 loci the size of the C. parvum and C. hominis repeats did not overlap. Assuming that C. parvum and C. hominis evolved from a common ancestor, these observations suggest a differential evolution of repeat length at these loci.
微小隐孢子虫和人隐孢子虫是两种形态相同的顶复门原生动物，可感染人类。尽管这两个物种的基因组有97%的相似度，但其宿主范围却显著不同。微小隐孢子虫可感染人类和动物，主要是一种人畜共患感染，而人隐孢子虫通常在动物中检测不到。这两个物种的遗传多态性程度已在当地进行了调查，但尚未在更大的地理范围内进行调查。在此，使用多个随机分布的微卫星和小卫星对一组无关的微小隐孢子虫和人隐孢子虫分离株进行基因分型。平均而言，由6 - 24个碱基对的串联重复序列基序组成的小卫星比微卫星具有更高的多态性。当将每个位点的微卫星和小卫星等位基因的平均数用作异质性的衡量标准时，未发现微小隐孢子虫和人隐孢子虫之间存在差异。然而，这两个物种的等位基因频率分布显著不同，在14个位点中的6个位点上，微小隐孢子虫和人隐孢子虫重复序列的大小没有重叠。假设微小隐孢子虫和人隐孢子虫是由一个共同祖先进化而来，这些观察结果表明这些位点上重复长度的进化存在差异。
