Biofilms on urban aquatic plastic pollution as a reservoir for pathogenic yeasts

ABSTRACT Pollution of aquatic environments is a concern and poses a health risk to aquatic and terrestrial life. Plastic pollutants act as surfaces to which microorganisms adhere, forming a community known as the plastisphere. Studies investigating the bacterial diversity of the plastisphere are plentiful, but less is known about the fungal communities, especially yeasts, within these biofilms. Given the increasingly recognised threat of yeast infections, it is important to investigate the environmental presence of potential pathogenic yeasts on possible vehicles that may contribute to their distribution. In this study, the fungal diversity of the plastisphere of various types of plastic polymers collected from an urban freshwater source was analysed, and possibly pathogenic yeast strains were identified. Isolates were also tested for susceptibility to the antifungal, fluconazole. Microscopy sheds light on the overall diversity found in the plastisphere, while metagenomic data revealed that fungal plastisphere communities are dominated by the phylum Ascomycota. Both metagenomic and culture-dependant analysis revealed the presence of possibly pathogenic yeast in the genera Candida (some with low fluconazole susceptibility) and Exophiala. This highlights the possibility that the plastisphere may harbour pathogenic yeasts and could contribute to their distribution in the environment and transmission between the environment and humans.