The larval and adult schistosomes can effectively establish the stable parasitic relationship with their final hosts and then maintain the parasitism for a long time,due to the successful adaptation to their parasitic lifestyle. This paper reviews the progress of research on parasitic adaptability of schistosomes in several respects,and demonstrates the application value of schisto-somal genes related to parasitic adaptability in schistosomiasis control and exploitation of natural active molecules.

OBJECTIVETo confirm the genetic relation between Giardia lamblia (G. lamblia) isolates from different geographic regions of China and other countries.

METHODSGenomic DNA were extracted from the trophozoites or cysts of Giardia lamblia. The triose phosphate isomerase (tim) gene was amplified using polymerase chain reaction (PCR) technique. PCR products were digested with endonuclease and sequenced. The data of sequencing were analyzed with the DNAstar software and compared with that of the isolates acquired from GenBank.

RESULTSOf nine isolates of Giardia lamblia from China (C1, C2, CH2 and CH3), Cambodia (CAM), Australia (A1 and A2) and America (BP and CDC), respectively, 3 (A1, A2 and CAM) fit into Group 1 (WB), 2 (CH2 and CH3)) into Group 2, and 4 (C1, C2, BP and CDC) into Group 3 (GS). The results confirmed the genetic relatedness of G. lamblia isolates from all over the world.

CONCLUSIONGenotyping isolates of G. Lamblia provides important information for establishing the phylogenetic relationship or for the epidemiological evaluation of the spreading of this organism.

Amino Acid Sequence ; Animals ; Base Sequence ; DNA, Protozoan ; chemistry ; Genotype ; Giardia lamblia ; classification ; enzymology ; genetics ; Polymerase Chain Reaction ; Restriction Mapping ; Triose-Phosphate Isomerase ; chemistry ; genetics

OBJECTIVETo investigate the intraspecific difference of the triose phosphate isomerase (tim) gene from Giardia lamblia (G. lamblia).

METHODSTotal genomic DNA of G. lamblia was extracted and partial fragments of the triose phosphate isomerase (tim) gene were amplified by polymerase chain reaction (PCR). All nucleotide sequences were analyzed by using a phylogenetic analysis, which was constructed with parsimony and Neighbor-joining (N-J) methods.

RESULTSA total of 124 variable sites (23% of all sequences detected) was defined, most of which were found at the silent sites of codons. Two similar phylogenetic trees were constructed, subdividing 16 Giardia isolates into two groups.

CONCLUSIONThe genetic diversity of G. lamblia appeared to be little affected by factors of both host and geography, while natural-selection played an important role in DNA molecular evolution level of the tim gene. The tim gene may be considered a very useful genetic marker of the population genetic structure of G. lamblia.

Animals ; Base Sequence ; DNA, Protozoan ; chemistry ; genetics ; Giardia lamblia ; enzymology ; genetics ; Molecular Sequence Data ; Phylogeny ; Polymerase Chain Reaction ; Sequence Alignment ; Sequence Analysis, DNA ; Sequence Homology, Nucleic Acid ; Species Specificity ; Triose-Phosphate Isomerase ; genetics

BACKGROUNDPyruvate phosphate dikinase (PPDK) reversibly catalyzes the interconversion of phosphoenolpyruvate (PEP) and pyruvic acid, leading to catabolism and adenosine triphosphate (ATP) synthesis or gluconeogenesis and ATP consumption. Molecular modeling of PPDKs from divergent organisms demonstrates that the orientation of the phosphorylatable histidine residue within the central domain of PPDK determines whether this enzyme promotes catabolism or gluconeogenesis. The goal of this study was to determine whether PDDK from Giardia underwent adaptive evolution in order to produce more energy under anaerobic conditions.

METHODSA total of 123 PPDK sequences from protozoans, proteobacteria, plants, and algae were selected, based upon sequence similarities to Giardia lamblia PPDK and Zea mays PPDK. Three-dimensional (3-D) models were generated for PPDKs from divergent organisms and were used to compare the orientation of the phosphorylatable histidine residue within the central domain of PPDKs. These PPDKs were compared using a maximum-likelihood tree.

RESULTSFor PPDK from Giardia, as well as from other anaerobic protozoans, the central domain tilted toward the N-terminal nucleotide-binding domain, indicating that this enzyme catalyzed ATP synthesis. Furthermore, the orientation of this central domain was determined by interactions between the N- and C-terminal domains. Phylogenetic analysis of the N- and C-terminal sequences of PPDKs from different species suggested that PPDK has likely undergone adaptive evolution in response to differences in environmental and metabolic conditions.

CONCLUSIONThese results suggested that PPDK in anaerobic organisms is functionally adapted to generate energy more efficiently in an anaerobic environment.

Adenosine Triphosphate ; metabolism ; Evolution, Molecular ; Giardia lamblia ; enzymology ; Protozoan Proteins ; chemistry ; classification ; genetics ; Pyruvate, Orthophosphate Dikinase ; chemistry ; classification ; genetics