Parasite genomes

Parasitic infections continue to bring misery and death to millions of people in developing countries, so it is encouraging that medicine is beginning to catch up with these persistent pests. Recently, by sequencing the entire genome of two particularly troublesome parasites, scientists have come one step closer to understanding how they tick, and figuring out how to stop then in their tracks.

Brugia malayiDraft Genome of the Filarial Nematode Parasite Brugia malayi
Science 2007 317: 1756-1760
Parasitic nematodes that cause elephantiasis and river blindness threaten hundreds of millions of people in the developing world. We have sequenced the 90 megabase (Mb) genome of the human filarial parasite Brugia malayi and predict 11,500 protein coding genes in 71 Mb of robustly assembled sequence. Comparative analysis with the free-living, model nematode Caenorhabditis elegans revealed that, despite these genes having maintained little conservation of local synteny during 350 million years of evolution, they largely remain in linkage on chromosomal units. More than 100 conserved operons were identified. Analysis of the predicted proteome provides evidence for adaptations of B. malayi to niches in its human and vector hosts and insights into the molecular basis of a mutualistic relationship with its Wolbachia endosymbiont. These findings offer a foundation for rational drug design.

Giardia lambliaGenomic minimalism in the early diverging, intestinal parasite, Giardia lamblia
Science 2007 317: 1921-1926
The genome of the eukaryotic protist Giardia lamblia, an important human intestinal parasite, is compact in structure and content, contains few introns or mitochondrial relics, and has simplified machinery for DNA replication, transcription, RNA processing, and most metabolic pathways. Protein kinases comprise the single largest protein class and reflect Giardia’s requirement for a complex signal transduction network for coordinating differentiation. Lateral gene transfer from bacterial and archaeal donors has shaped Giardia’s genome, and previously unknown gene families, for example, cysteine-rich structural proteins, have been discovered. Unexpectedly, the genome shows little evidence of heterozygosity, supporting recent speculations that this organism is sexual. This genome sequence will not only be valuable for investigating the evolution of eukaryotes, but will also be applied to the search for new therapeutics for this parasite.

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3 Responses to Parasite genomes

  1. Eileen says:

    Please, I have a question about protists (which is slightly off topic, but you mentioned Giardia’s being a protist).

    OK, I teach third-grade science, where protists are mentioned. Never having studied them in high-school biology, my best understanding (simply) is that while they seem to have both plant and animal characteristics (such as sometimes being able to manufacture some of their own food, like a plant, yet being also able to move around) they fall clearly into neither the plant nor animal kingdoms.

    Is this correct? Do scientists not know where to classify protists, or are they considered a third category, neither plant, nor animal. I always feel so inadequate with my third-graders trying to explain this, yet our text book explains it even less! Can you help?


  2. ajcann says:

    The Wikipedia explanation is very good:

    The term protista was coined in 1866 and these organisms do not have much in common other than being relatively simple eukaryotes, so these days they are thought of as protozoa (animal-like protists), algae (plant-like protists) or fungus-like protists. For a more detailed explanation, see Kingdoms, the 2nd broadest category in biological taxonomy:

  3. mike says:

    Does anyone know the latest research on river blindness with relationship to wolbachia and onchocerca vulvulus?

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