THE IDENTIFICATION AND PHYLOGENETIC RELATIONSHIP OF PATHOGENIC SPECIES OF ASPERGILLUS BASED ON THE MITOCHONDRIAL CYTOCHROME-B GENE

To study the identification and phylogeny of pathogenic isolates of As pergillus, we designed primers from known cytochrome b amino acid sequ ences. Using these primers, 426 bp fragments of a mitochondrial (mt) c ytochrome b gene were amplified by polymerase chain reaction (PCR), di rectly sequenced, and compared among Aspergillus fumigatus, A. flavus, A. niger, A. terreus and Emericella nidulans. Except for E. nidulans, all strains produced the 426 bp fragment by PCR. The E. nidulans stra ins demonstrated both an intron-presence fragment (approximate to 1500 bp) and intron-absence fragment (426 bp). Species-specific nucleotide s were found in each of the five species. Based on sequence analysis, the strains were further divided into several groups within each speci es. When a 142-amino-acid sequence was estimated from the 426 bp nucle otide sequence using the yeast mt genetic code, the amino acid sequenc es showed no difference among strains of the individual species. DNA-b ased phylogenetic and amino acid-based trees were constructed. In conc lusion, the DNA sequences of the cytochrome b gene may be of use in id entification of pathogenic Aspergillus species and the amino acid-base d tree suitable for discussing their phylogenetic relationships.