Full text loading...
Chapter 20 : Giardia lamblia: Molecular Studies of an Early Branching Eukaryote
Category: Applied and Industrial Microbiology; Food Microbiology
Ebook: Choose a downloadable PDF or ePub file. Chapter is a downloadable PDF file. File must be downloaded within 48 hours of purchase
This chapter provides an update on Giardia genome research and highlights studies that utilized genomics and functional genomics to understand the phylogeny, biochemistry, molecular biology, and epidemiology of Giardia lamblia. Earlier observations of a highly compact G. lamblia genome containing a disproportionate number of genes coding for variant surface proteins (VSPs), structural proteins, and ribosomal RNA have been confirmed by genomewide sequence analysis. Many cellular processes of G. lamblia (e.g., DNA replication, transcription, and RNA processing), as well as metabolic pathways, are simple compared to higher eukaryotes. To ensure its survival inside and outside its host, G. lamblia must exert precise control over the transcription of genes involved in encystation, excystation, and trophozoite replication. RNA polymerases and transcription initiation factors are similar in some respects to those in eukaryotes but also contain peptides unique to Giardia. G. lamblia is of special interest to those attempting to understand eukaryotic evolution. Transfection of CHO cells with a second cyst wall protein (cwp2) promoter region fused to the gene for firefly luciferase was used to study regulation of cwp2 transcription by sterol regulatory element binding proteins (SREBPs). This study showed that, in the absence of cholesterol, cwp2 transcription was increased and that SREBP binds to the cwp2 promoter to activate transcription of this cyst wall protein. A third cyst wall protein (cwp3) was identified by searching the G. lamblia database with amino acid sequence of a first cyst wall protein (cwp1) and cwp2 leucinerich repeat regions.