Morphological and Genotypic Identification of Some Environmental Isolates of Aspergillus in Iran Based on Beta-Tubulin Gene Sequencing

The genus Aspergillus is a mold consisting of various groups and species. Species identification of these fungi is important from pathogenic, toxigenic and industrial points of view. Conventional laboratory methods for delineation of Aspergillus species are based on macro- and microscopic characteristics of the colonies. These methods are time consuming and need expert technicians. The present study aimed to use beta tubulin (BT2) gene sequencing, in conjunction with morphological data, for species identification of Aspergillus strains isolated from some environments in Iran. Totally, about 200 Aspergillus strains, isolated from soils and air samples of different environments including hospitals, public and natural places, were used. All isolates were subcultured on Sabouraud dextrose agar and Czapec Dox agar. They were preliminarily identified based on micro slide-culture. Genomic DNA was extracted from all strains by a conical grinder and BT2 gene was amplified by polymerase chain reaction (PCR) from each sample. Among them, nucleotide sequences of 21 isolates, as representatives of morphologic features, were determined. The obtained data was analyzed via comparison with sequences existed in GenBank database. Among the 21 Aspergillus sequenced isolates, seven isolates were identified as Aspergillus flavus, 3 as Aspergillus fumigatus, 3 as Aspergillus chevalieri, 2 as Aspergillus tubingensis, 2 as Aspergillus niveoglacus, 2 as Aspergillus rubber, one as Aspergillus niger and one as Aspergillus versicolor. Morphological results were confirmed by genotypic data. The findings of this study indicated that sequencing beta tubulin gene is a valuable tool for species identification of Aspergillus environmental isolates. This method was found to be more valid in comparison with morphological analysis. Further studies with application of other genetic markers and molecular DNA-based procedures on discrimination of Aspergillus species are recommended.