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Is human giardiasis caused by two different Giardia species?
Jon Jerlström-Hultqvist1, Johan Ankarklev, Staffan G Svärd
1Department of Cell and Molecular Biology, BMC, Uppsala University, Uppsala, Sweden.
Gut Microbes
|April 7, 2011
Summary
Giardia intestinalis genomes reveal significant genetic differences between human and animal strains. These findings support the classification of human Giardia into two distinct species, impacting parasite research and treatment.
Area of Science:
- Genomics
- Parasitology
- Molecular Biology
Background:
- Giardia intestinalis is a leading cause of parasitic diarrheal disease worldwide.
- Previous genomic studies revealed genetic divergence between human-associated assemblages A and B.
- Understanding Giardia genetic diversity is crucial for effective control strategies.
Purpose of the Study:
- To compare the genomes of human Giardia intestinalis assemblages A and B with a hoofed-animal assemblage E isolate.
- To identify conserved and variable gene families and chromosomal rearrangements across different Giardia assemblages.
- To investigate the genetic basis for the distinct host associations of Giardia.
Main Methods:
- Whole-genome sequencing of Giardia intestinalis assemblage E isolate P15.
- Comparative genomic analysis of assemblage A (WB), assemblage B (GS.1), and assemblage E (P15) isolates.
- Analysis of orthologous protein identity and gene content.
- Detection of chromosomal rearrangements.
Main Results:
- Average amino acid identity between human assemblages A and B was 78%, with significant differences in variable gene families.
- A conserved core genome of 4,557 genes (91%) was identified across all isolates.
- Assemblage E and A isolates showed higher amino acid similarity than two human isolates (A and B).
- Extensive chromosomal rearrangements were observed, even within chromosomes.
Conclusions:
- Giardia intestinalis exhibits substantial genomic variation, particularly in assemblage-specific genes.
- The genetic similarity between assemblage E and A supports the hypothesis of distinct Giardia species infecting humans.
- Further research into Giardia genomics can refine classification and inform therapeutic approaches.
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