title: A comparison of the Giardia lamblia trophozoite and cyst transcriptome using microarrays.
abstract: BACKGROUND
  Compared with many protists, Giardia lamblia has a simple life cycle alternating between cyst and trophozoite. Most research on the molecular biology of Giardia parasites has focused on trophozoites and the processes of excystation and encystation, whereas cysts have attracted less interest. The striking morphological differences between the dormant cyst and the rapidly dividing and motile trophozoite implies profound changes in the metabolism as the parasite encysts in the host's intestine and excysts upon ingestion by a new host.
  
  
  RESULTS
  To investigate the magnitude of the transcriptional changes occurring during the G. lamblia life cycle we compared the transcriptome of G. lamblia trophozoites and cysts using single-color oligonucleotide microarrays. Cysts were found to possess a much smaller transcriptome, both in terms of mRNA diversity and abundance. Genes encoding proteins related to ribosomal functions are highly over-represented. The comparison of the transcriptome of cysts generated in culture or extracted from feces revealed little overlap, raising the possibility of significant biological differences between the two types of cysts.
  
  
  CONCLUSIONS
  The comparison of the G. lamblia cyst and trophozoite transcriptome showed that transcripts of most genes are present at a lower level in cysts. This global view of the cyst and trophozoite transcriptome complements studies focused on the expression of selected genes during trophozoite multiplication, encystation and excystation.
authors.affiliation: Division of Infectious Diseases, Tufts Cummings School of Veterinary Medicine, 200 Westboro Road, North Grafton, MA, USA.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Faghiri
authors.forename: Giovanni
authors.initials: G
authors.lastname: Widmer
mesh_terms: D020869:Gene Expression Profiling; D016829:Giardia lamblia / Q000235:genetics* / Q000378:metabolism; D046228:Microarray Analysis; D033761:Spores, Protozoan / Q000235:genetics* / Q000378:metabolism*; D053058:Trophozoites / Q000378:metabolism*