Culturable yeast diversity in urban topsoil influenced by various anthropogenic impacts.

In urban ecosystems, processes associated with anthropogenic influences almost always lead to changes in soil micromycete complexes. The taxonomic structure of soil micromycete complexes is an important informative parameter of soil bioindication in the ecological control of urban environments. Unicellular fungi, such as culturable yeasts, are a very suitable and promising object of microbiological research for monitoring urban topsoil. This review aims to give an overview of the yeast communities in urban topsoil in different areas of Moscow (heating main area, household waste storage and disposal area, highway area) and to discuss the changes in the taxonomic structure of culturable yeast complexes depending on the type and intensity of anthropogenic impact.

Enterobacteriaceae in soils and atmospheric dust aerosol accumulations of Moscow city.

The topsoils and atmospheric dust aerosols of the various areas of the city of Moscow were studied. Most of the dust samples contained a considerable number of particles enriched in phosphorus - a sign of contamination by feces. A variety of Enterobacteriaceae species, including opportunistic and pathogenic species, were isolated from the topsoil and dust samples and identified using 16S rDNA nucleotide sequences: Enterobacter aerogenes, E. agglomerans, E. cloacae, E. kobei, E. nimipressuralis, Escherichia coli, Citrobacter europaeus, Klebsiella granulomatis, K. grimontii, K. oxytoca, K. quasipneumoniae, K. variicola, Kluyvera ascorbate, Kluyvera intermedia, Leclercia adecarboxylata, Salmonella enterica and Trabulsiella guamensis. The greatest diversity of pathogens was isolated from spring soil and dust samples immediately after spring snowmelt. Antibiotic resistance of the isolated E. coli strains was tested using disks with a wide range of antimicrobial drugs: Amoxicillin, Ampicillin, Meropenem, Pefloxacin, Streptomycin, Ticarcillin+clavulanic acid, Fosfomycin, Ceftibuten, Ciprofloxacin. Resistance was observed in more than 22% of E. coli strains. The traffic area had a significant number of antibiotic-resistant E. coli strains, clearly indicating a high health risk from soil and dust exposure.

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.