Molecular characterization of non-Cryptococcus yeast communities isolated from Eucalyptus trees

Plants are crucial habitats for fungus communities as they provide an appropriate physical environment for the growth and reproduction of the yeast microbiome. Varieties of pathogenic and non-pathogenic yeast could be found in Eucalyptus trees. Although Cryptococcus species are the most common pathogenic yeasts associated with Eucalyptus trees, other yeasts also grow on trees and are critical to human health. This study aimed to identify the yeast species associated with Eucalyptus trees.

In total, 107 yeast species were collected from Eucalyptus trees and subsequently identified through both molecular and traditional techniques. Genomic DNA extraction was performed using the boiling method. The internal transcribed spacer region of the ribosomal DNA was amplified utilizing the polymerase chain reaction (PCR) technique, followed by the purification and sequencing of the PCR products to identify the isolates.

Yeast strains belonged to 12 genera and 26 species of both the Ascomycete and Basidiomycete phyla. The most frequent species were Rhodotorula mucilaginosa (24.2%), Candida tropicalis (15%), Candida guilliermondii (11.2%), and Aureobasidium pullulans (10.2%).

In this study, most of the yeast isolates, such as Candida and Trichosporon, were important to human health. Eucalyptus trees, as part of the natural flora, could be considered an environmental reservoir for yeasts, in which they can survive, disperse to the surrounding environment, and become a potential infectious source affecting public health.