National Institute of Public Health and Environment (RIVM), Laboratory for Zoonosis and Environmental Microbiology (CIb-LZO), P.O. Box 1, 3720, BA, Bilthoven, The Netherlands.
Parasit Vectors. 2012 Aug 10;5:168. doi: 10.1186/1756-3305-5-168.
Giardia duodenalis is a common protozoan parasite of humans and animals. Genetic characterization of single loci indicates the existence of eight groups called assemblages, which differ in their host distribution. Molecular analyses challenged the idea that G. duodenalis is a strictly clonal diplomonad by providing evidence of recombination within and between assemblages. Particularly, inter-assemblage recombination events would complicate the interpretation of multi-locus genotyping data from field isolates: where is a host infected with multiple Giardia genotypes or with a single, recombined Giardia genotype.
Population genetic analyses on the single and multiple-locus level on an extensive dataset of G. duodenalis isolates from humans and animals were performed.
Our analyses indicate that recombination between isolates from different assemblages are apparently very rare or absent in the natural population of Giardia duodenalis. At the multi-locus level, our statistical analyses are more congruent with clonal reproduction and can equally well be explained with the presence of multiple G. duodenalis genotypes within one field isolate.
We conclude that recombination between G. duodenalis assemblages is either very rare or absent. Recombination between genotypes from the same assemblage and genetic exchange between the nuclei of a single cyst needs further investigation.
十二指肠贾第鞭毛虫是一种常见的人类和动物原生动物寄生虫。单一基因座的遗传特征表明存在 8 个称为聚集的群组，它们在宿主分布上存在差异。分子分析通过提供聚集内和聚集间重组的证据，对贾第鞭毛虫是严格的无性二倍体的观点提出了挑战。特别是，聚集间重组事件会使对来自野外分离株的多基因座基因分型数据的解释复杂化：一个宿主感染了多种贾第鞭毛虫基因型还是单一重组的贾第鞭毛虫基因型。
对来自人类和动物的广泛贾第鞭毛虫分离株的单基因座和多基因座数据集进行了种群遗传分析。
我们的分析表明，不同聚集的分离株之间的重组在自然种群中的十二指肠贾第鞭毛虫中显然非常罕见或不存在。在多基因座水平上，我们的统计分析更符合无性繁殖，并且同样可以用一个野外分离株中存在多种贾第鞭毛虫基因型来解释。
我们得出结论，聚集间的重组是非常罕见或不存在的。同一聚集的基因型之间的重组和单个胞囊核之间的遗传交换需要进一步研究。
