Department Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
BMC Microbiol. 2022 Jun 27;22(1):166. doi: 10.1186/s12866-022-02581-3.
Giardia duodenalis, a single-celled intestinal parasite, is divided into eight assemblages (A-H), with differences in host specificity. Giardia duodenalis reproduces asexually and cycles between the binucleated trophozoite (4 N) and the infectious cyst with four nuclei (16 N). Interaction between the nuclei is limited. Therefore, genetic drift causes differences in genetic make-up between the non-daughter nuclei; the allelic sequence heterozygosity (ASH). The ASH is low (0.01%-0.0023%) for the related assemblages A and E, higher (0.43-0.53) for assemblage B and much higher (0.74% -0.89%) for the assemblage C and D at the root of the phylogenetic tree. The heterozygosity in assemblage F, in the same clade as assemblage A and E, was unknown. The heterozygosity in the sequences of the gdh and dis3 genes was used as proxy for the ASH and whole genome amplification of single cysts followed by cloning and Sanger sequencing of dis3 fragment could reveal the genetic variation within the cyst. The aim of the study was to determine the level of heterozygosity within pooled and single cysts of different assemblages.
The heterozygosity in gdh and dis3 was determined in pooled cysts of the assemblages A to F. Heterozygosity in the isolates of the assemblages C (n = 2) and D (n = 1) ranged from 0.41% to 0.82% for gdh and dis3 and no heterozygosity was found in the isolates of the assemblages A (n = 4), E (n = 3) and F (n = 3). The heterozygosity in assemblage B (n = 7) was intermediate (0% to 0.62%). Next, the number of haplotypes of dis3 was determined for single cysts of assemblages C, D and E. In the assemblages C and D, two to four haplotypes were found per cyst, while in assemblage E only one haplotype was identified.
Having high heterozygosity is characteristic for the assemblages C and D, while having a low heterozygosity is characteristic for the clade with the assemblages A, E and F. Presence of more than 1 haplotype per cyst in assemblage C and D suggests differences between the non-daughter nuclei, in contrast to the one haplotype in assemblage E.
肠道寄生虫贾第虫分为 8 个集合体（A-H），具有不同的宿主特异性。贾第虫通过有丝分裂无性繁殖，并在双核营养体（4N）和具有四个核的感染性囊（16N）之间循环。核之间的相互作用有限。因此，遗传漂变导致非子核之间的遗传结构存在差异；等位序列异质性（ASH）。相关集合体 A 和 E 的 ASH 较低（0.01%-0.0023%），集合体 B 较高（0.43-0.53），系统发育树根部的集合体 C 和 D 则更高（0.74%-0.89%）。与集合体 A 和 E 同属一个分支的集合体 F 的异质性未知。gdh 和 dis3 基因序列的异质性可用作 ASH 的替代物，对单个囊的全基因组扩增，然后对 dis3 片段进行克隆和 Sanger 测序，可以揭示囊内的遗传变异。本研究的目的是确定不同集合体的混合和单个囊的异质性水平。
确定了集合体 A 至 F 的混合囊中的 gdh 和 dis3 的异质性。集合体 C（n=2）和 D（n=1）的分离株的 gdh 和 dis3 的异质性范围为 0.41%-0.82%，而集合体 A（n=4）、E（n=3）和 F（n=3）的分离株中未发现异质性。集合体 B（n=7）的异质性处于中间水平（0%至 0.62%）。接下来，确定了集合体 C、D 和 E 的单个囊的 dis3 单倍型数量。在集合体 C 和 D 中，每个囊有 2 到 4 个单倍型，而在集合体 E 中只鉴定出一个单倍型。
高异质性是集合体 C 和 D 的特征，而低异质性是集合体 A、E 和 F 分支的特征。集合体 C 和 D 中每个囊有多个单倍型，而集合体 E 中只有一个单倍型，这表明非子核之间存在差异。
