Microplastic particles in the soil not only pollute the environment, they could also pose a health risk. Researchers have found numerous types of fungus on them, including many pathogenic species. Apparently microplastics offer them a new ecological niche and thus represent a source of fungal infections that can affect humans, animals and plants. This is particularly problematic in view of the fact that the tiny plastic particles can spread widely with the wind and thus bring pathogens into new areas.
Microplastics are widespread around the world. The tiny plastic particles have already been detected in the deep sea and on remote mountain peaks, are ubiquitous in the soil and also accumulate in the human body. While direct health effects are still unclear, it has already been found that these plastics are colonized by numerous microorganisms in the environment. Researchers have therefore now referred to the microplastic habitat as the “plastisphere”. The scientific focus so far has been on bacteria, however, and mainly microplastic particles from water samples have been examined.
Mushrooms on plastic
A team led by Gerasimos Gkoutselis from the University of Bayreuth has now dealt with fungi on microplastics in the soil. “Fungi are the ideal group of organisms for studying the microbial colonization of plastics in terrestrial systems because they are particularly well adapted to life in the plastisphere,” the researchers write. In order to get the most practical picture possible, they selected soil samples for their investigation from areas in the immediate human environment: In the western Kenyan city of Siaya, they took samples from a market square, two garbage dumps, on the roadside and in an inner courtyard.
With the help of various microscopic methods and an analysis of the metagenome, Gkoutselis and his colleagues examined which fungi were found on the plastic particles. The result: “We were able to observe all stages of fungal biofilm formation on the microplastic particles. We were able to prove that the fungi not only grow in the so-called plastisphere, but also multiply. The data that we have obtained from microscopic examinations and DNA analyzes provide reason to assume that microplastics in the soil are populated by fungi across the board. “
Pathogens preferred
According to the analysis, the fungal communities on the microplastic particles differed significantly from those in the surrounding soil – in favor of certain pathogenic species. “Some species that are dangerous to humans, including black fungi and cryptococcal yeasts, are present in higher concentrations on the surfaces of the microplastic particles than in the surrounding soil,” reports Gkoutselis. “Our study therefore justifies the finding that microplastics in the soil are a possible source of fungal infections.”
According to the researchers, the reason why pathogenic fungi are increasingly found on the microplastic particles is that the pathogenic species have certain properties that make it easy for them to colonize the actually inhospitable plastic surface: “They produce invasive structures, form biofilms and settle Slime free, ”said the researchers. Although they only analyzed soil samples from Kenya for the current study, based on these properties they assume that this is a global phenomenon.
Worldwide problem
“Given the increasing amount of plastic waste in terrestrial ecosystems around the world, this correlation can have serious consequences for the global epidemiology of fungal infections,” warn the researchers. The problem is exacerbated by the fact that the plastic particles spread easily: “The long-lasting substrates can not only serve as a reservoir for pathogens, but can also be transported over long distances by wind, currents and waves and ultimately lead to the establishment of foreign microbial communities in new places. “
Fungal infections are increasing worldwide and are responsible for numerous deaths, especially in tropical regions. “The present study is the first to demonstrate the direct influence of plastic pollution on the accumulation of pathogens in the soil,” the authors write. “Future studies should analyze both the environmental and epidemiological consequences of these highly likely global phenomena, while policymakers should consider classifying plastic waste as a potential threat to human health.”
Source: Gerasimos Gkoutselis (University of Bayreuth, Germany) et al., Scientific Reports, doi: 10.1038 / s41598-021-92405-7