Phylogenetic analysis ofCryptosporidiumisolates in Henan

AbstractThe functional mitochondrial protein alternative oxidase (AOX) gene was used as a marker to analyse the phylogenetic relationship betweenCryptosporidiumisolates. This gene was characterized, and the phylogentic tree was established fromCryptosporidiumisolates and compared to those generated from 18S rRNA and heat-shock protein 70 (HSP70) gene sequences. The present trial aimed at finding out whether the AOX gene is suitable for phylogenetic analysis of theCryptosporidiumgenus. The results revealed that the genusCryptosporidiumcontained the phylogenetically distinct speciesC. parvum,C. hominis,C. suisandC. baileyi, which were consistent with the biological characterization and host specificity reported earlier.Cryptosporidiumspecies formed two clades: one includedC. hominis,C. suis,C. parvumcattle genotypes andC. parvummouse genotype; and the other comprisedC. meleagridisandC. baileyiisolates. WithinC. parvum, both the mouse genotype and the pig genotype I (also known asC. suis) isolates differed from cattle and human (also known asC. hominis) genotypes, based on the aligned nucleotide sequences. The sequence identity of the AOX gene was higher betweenC. meleagridisandC. baileyithan betweenC. meleagridisandC. parvum. The phylogenetic trees showed thatC. meleagridiswas closer toC. baileyithan toC. parvum. This result was inconsistent with the phylogenetic analysis deduced from 18S rRNA and HSP70 gene sequences, respectively. The present results suggest that the AOX gene is not only equally suitable for the phylogenetic analysis ofCryptosporidium, but also provides an outstanding and new approach in determiningCryptosporidiumheredity.