Phylogenetic analysis of Cryptosporidium isolates in Henan

The mitochondrial functional protein alternative oxidase(AOX)gene was used as the marker for analysing phylogentic relationship of the Cryptosporidium isolates.The AOX genes were characterized,and the phylogentic tree was established from the Cryptosporidium isolates,and compared with that of 18S rRNA and HSP70 gene sequences,then determined whether the AOX gene was suitable for phylogentic analysis of the genus of Cryptosporidium or not.The results revealed that the genus Cryptosporidium contained the phylogenetical distinct species C.parvum,C.hominis,C.suis and C.baileyi,which were consistent with the biological characteristics and host specificity up to date.The Cryptosporidium species formed two clades,one included C.hominis,C.suis,C.parvum cattle genotype and C.parvum mouse genotype and the other included C.meleagridis and C.baileyi isolates.Within C.parvum,both the mouse genotype isolate and the pig genotypeⅠ(already known as C.suis)isolate differed from cattle genotype and human genotype(already known as C.hominis)based on the nucleotide sequences alignment.The identity of the AOX gene sequences between C.meleagridis and C.baileyi was more distinguishedly than that of between C.meleagridis and C.parvum,and the phylogentic trees showed that C.meleagridis had a closer phylogenetic affinity with the C.baileyi than that with C.parvum,this result was inconsistent with the phylogentic analysis results from 18S rRNA and HSP70 gene sequences,respectively.Present result suggested that the AOX gene is not only equally suitable for the phylogentic analysis of Cryptosporidium,but also provides an approach to identify new genes heredity of Cryptosporidium.