Changes in urban soil yeast communities after a reduction in household waste during the COVID-19 pandemic

The soils of streets, urban parks and suburban areas were examined for yeasts in the summer of 2020 on the territory of the southern cities of Russia and the Republic of Crimea: Krasnodar, Maykop, Sochi and Simferopol. The results of this study are compared with the results of a previous study carried out in these cities in 2019. This study was conducted three months after the lockdown due to the COVID-19 pandemic, which led to a sustained decline in household waste deposition in these areas. The number of tourists visiting these southern cities decreased significantly, and the number of walkers and visitors to urban parks fell sharply. In 2020, after the decline of household waste loads, the yeast abundance was slightly but reliably higher than in 2019. A total of 30 yeast species were observed - 11 ascomycetes and 19 basidiomycetes. This was more than in 2019 and was caused by twice as many autochthonous basidiomycetous yeast species (natural core community), which were found in urban soils only after the reduction in household waste in the environment - Apiotrichum dulcitum, A. laibachii, Saitozyma podzolica Solicoccozyma terricola. And at the same time, the proportion of clinically significant (opportunistic) yeasts, Candida sake and Meyerozyma guilliermondii, was much lower in 2020 than in 2019. Thus, the observed changes in yeast communities in urban soils could be a short-time response of the microbial community to a reduction in household waste.