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The compact genome of Giardia muris reveals important steps in the evolution of intestinal protozoan parasites.

ABSTRACT: Diplomonad parasites of the genus Giardia have adapted to colonizing different hosts, most notably the intestinal tract of mammals. The human-pathogenic Giardia species, Giardia intestinalis, has been extensively studied at the genome and gene expression level, but no such information is available for other Giardia species. Comparative data would be particularly valuable for Giardia muris, which colonizes mice and is commonly used as a prototypic in vivo model for investigating host responses to intestinal parasitic infection. Here we report the draft-genome of G. muris. We discovered a highly streamlined genome, amongst the most densely encoded ever described for a nuclear eukaryotic genome. G. muris and G. intestinalis share many known or predicted virulence factors, including cysteine proteases and a large repertoire of cysteine-rich surface proteins involved in antigenic variation. Different to G. intestinalis, G. muris maintains tandem arrays of pseudogenized surface antigens at the telomeres, whereas intact surface antigens are present centrally in the chromosomes. The two classes of surface antigens engage in genetic exchange. Reconstruction of metabolic pathways from the G. muris genome suggest significant metabolic differences to G. intestinalis. Additionally, G. muris encodes proteins that might be used to modulate the prokaryotic microbiota. The responsible genes have been introduced in the Giardia genus via lateral gene transfer from prokaryotic sources. Our findings point to important evolutionary steps in the Giardia genus as it adapted to different hosts and it provides a powerful foundation for mechanistic exploration of host-pathogen interaction in the G. muris-mouse pathosystem.

SUBMITTER: Xu F

PROVIDER: S-EPMC7641422 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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The compact genome of Giardia muris reveals important steps in the evolution of intestinal protozoan parasites.

Xu Feifei F Jiménez-González Alejandro A Einarsson Elin E Ástvaldsson Ásgeir Á Peirasmaki Dimitra D Eckmann Lars L Andersson Jan O JO Svärd Staffan G SG Jerlström-Hultqvist Jon J

Microbial genomics 20200703 8

Diplomonad parasites of the genus Giardia have adapted to colonizing different hosts, most notably the intestinal tract of mammals. The human-pathogenic Giardia species, Giardia intestinalis, has been extensively studied at the genome and gene expression level, but no such information is available for other Giardia species. Comparative data would be particularly valuable for Giardia muris, which colonizes mice and is commonly used as a prototypic in vivo ...[more]

PMID: 32618561

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Project description:Cryptosporidiosis and giardiasis are recognized as significant enteric diseases due to their long-term health effects in humans and their economic impact in agriculture and medical care. Molecular analysis is essential to identify species and genotypes causing these infectious diseases and provides a potential tool for monitoring. This study uses information on species and genetic variants to gain insights into the geographical distribution and spatial patterns of Cryptosporidium and Giardia parasites. Here, we describe the population heterogeneity of genotypic groups within Cryptosporidium and Giardia present in New Zealand using gp60 and gdh markers to compare the observed variation with other countries around the globe. Four species of Cryptosporidium (C. hominis, C. parvum, C. cuniculus and C. erinacei) and one species of Giardia (G. intestinalis) were identified. These species have been reported worldwide and there are not unique Cryptosporidium gp60 subtype families and Giardia gdh assemblages in New Zealand, most likely due to high gene flow of historical and current human activity (travel and trade) and persistence of large host population sizes. The global analysis revealed that genetic variants of these pathogens are widely distributed. However, genetic variation is underestimated by data biases (e.g. neglected submission of sequences to genetic databases) and low sampling. New genotypes are likely to be discovered as sampling efforts increase according to accumulation prediction analyses, especially for C. parvum. Our study highlights the need for greater sampling and archiving of genotypes globally to allow comparative analyses that help understand the population dynamics of these protozoan parasites. Overall our study represents a comprehensive overview for exploring local and global protozoan genotype diversity and advances our understanding of the importance for surveillance and potential risk associated with these infectious diseases.

Project description:BackgroundIntestinal protozoan infections are confirmed as major causes of diarrhea, particularly in children, and represent a significant, but often neglected, threat to public health. No recent data were available in Lebanon concerning the molecular epidemiology of protozoan infections in children, a vulnerable population at high risk of infection.Methodology and principal findingsIn order to improve our understanding of the epidemiology of intestinal pathogenic protozoa, a cross-sectional study was conducted in a general pediatric population including both symptomatic and asymptomatic subjects. After obtaining informed consent from the parents or legal guardians, stool samples were collected in January 2013 from 249 children in 2 schools in Tripoli, Lebanon. Information obtained from a standard questionnaire included demographic characteristics, current symptoms, socioeconomic status, source of drinking water, and personal hygiene habits. After fecal examination by both microscopy and molecular tools, the overall prevalence of parasitic infections was recorded as 85%. Blastocystis spp. presented the highest infection rate (63%), followed by Dientamoeba fragilis (60.6%), Giardia duodenalis (28.5%) and Cryptosporidium spp. (10.4%). PCR was also performed to identify species and genotypes of Cryptosporidium, subtypes of Blastocystis, and assemblages of Giardia. Statistical analysis using a logistic regression model showed that contact with family members presenting gastrointestinal disorders was the primary risk factor for transmission of these protozoa.ConclusionsThis is the first study performed in Lebanon reporting the prevalence and the clinical and molecular epidemiological data associated with intestinal protozoan infections among schoolchildren in Tripoli. A high prevalence of protozoan parasites was found, with Blastocystis spp. being the most predominant protozoans. Although only 50% of children reported digestive symptoms, asymptomatic infection was observed, and these children may act as unidentified carriers. This survey provides necessary information for designing prevention and control strategies to reduce the burden of these protozoan infections, especially in children.

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The compact genome of Giardia muris reveals important steps in the evolution of intestinal protozoan parasites.

Publications

The compact genome of <i>Giardia muris</i> reveals important steps in the evolution of intestinal protozoan parasites.

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