Microplastic as spreader of fungal pathogens

, Gkoutselis Gerasimos, Rohrbach Stephan, Harjes Janno, Brachmann Andreas, Horn Marcus, Rambold Gerhard.

Microplastic (MP) has become a pervasive and persistent pollutant in nature, where it constitutes a micro-ecosystem for a diversity of microorganisms, the so-called plastisphere. Through the attachment of microbes, these floating artificial substrates implicate the enrichment and vectoring of potential pathogens, thereby interfering with the ecosystem functioning and threatening human health. However, microbial ecotoxicology of MP has been exclusively investigated in aquatic systems, although soil is the major sink for plastics and the main reservoir for a variety of microbes. Developing countries suffer particularly from environmental plastic pollution. Aggravatingly, destructive fungal pathogens are highly abundant in tropical soils, where they contribute substantially to human morbidity and mortality. Although developing countries in tropical regions, i.e. Subsaharan Africa, are particularly vulnerable to microbial ecotoxicology of MP, epiplastic communities remain alarmingly underexplored in those areas. In fact, no studies of plastic-associated microbial consortia from African environmental samples exist to date, nor molecular studies of the terrestrial plastisphere with a focus on fungi. Here, we grant first insights into the plastisphere of terrestrial MP and explore the role of MP debris as selective micro-habitats of soil fungi within the city boundary of Siaya, Kenya. Soil samples were collected from plastic waste accumulations from landfills and MPs separated from soil particles in an interposed subsampling step. ITS metabarcoding and multivariate analysis indicated a diverse fungal plastisphere compositionally distinct from the surrounding soil. Scanning electron microscopy (SEM) revealed massive quantities of plastic-attached spores and hyphae. Based on assignment analyses of trait data obtained from various sources, we highlight that soil-borne MP hosts and even concentrates a variety of phyto-, zoo- as well as opportunistic human pathogenic fungi. Our findings emphatically substantiate the need for a deeper and more comprehensive understanding of plastic pollution and its ecological implications in terrestrial ecosystems and for human health.

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