The distribution, colonization, and biodegradation of primary and secondary microplastics, as well as were effect on the plastisphere ecological systems, are analyzed. The pathways of microplastic contamination of the atmosphere, hydrosphere, and lithosphere are described. The composition of multispecies communities colonizing the microplastics and their differences from environmental communities unassociated with plastic within the same habitat are considered. The processes of microplastic biodegradation and their role as vectors for transfer of genetic information affecting the structure of natural microbial communities and for the propagation of toxic components are discussed.

A series of biocide-containing polyethylene composites were obtained using novel guanidine-containing copolymers immobilized on an inert mineral carrier. Multispecies microbial communities were isolated from the surface of polyethylene samples either incubated or found in the environment, and their taxonomic composition was determined. Biofilms reconstructed using microorganisms obtained from different ecotopes were shown to intensively foul polyethylene surfaces. The presence of polyguanidine biocide suppressed the growth and survival of both binary and multispecies biofilms, with a cumulative effect during long-term incubation. When microorganisms were co-cultivated in binary biofilms, the phenomenon of a decrease in biocide effectiveness was demonstrated. This protective effect is potentially based on cooperative interactions inside the binary biofilm community. Scanning electron microscopy showed a pronounced difference in the architecture of reconstructed biofilms incubated in the presence of biocide in comparison to control samples, where biocide suppressed the formation of dense and well-organized three-dimensional structures. Biofilm disruption by immobilized biocides occurred primarily during the later stages of biofilm formation, probably caused by polycation interaction with their negatively charged extracellular components.

The effect of humic acids on the formation of multispecies biofilms on the surface of high-pressure polyethylene and on the initial stages of its biocorrosion has been studied. The ability to form biofilms on the polyethylene surface and the initial stages of its biodegradation have been analyzed for two bacterial communities (binary and multispecies) isolated from the surface of polyethylene incubated in the topsoil (0–5-cm layer) in Myanmar during 180 days. Polyethylene samples were transported under sterile conditions to a laboratory (Moscow) and placed in vials with liquid medium (LB diluted 50 times by mineral medium M9 and with 0.1% C₁₁–C₁₆ paraffin solution added as an additional carbon source). Cultures were then disseminated to obtain individual colonies. Humic acids were extracted by alkaline extraction from the upper horizons of ferrallitic soil, in which the polyethylene sample was incubated (Myanmar), and from typical chernozem sampled in Lipetsk oblast (Orthic Acrisol and Haplic Chernozem according to the World Reference Base for Soil Resources, 2014). Humic acids were extracted from humate fertilizer Fleksom based on lowland peat. We assessed the formation of biofilms on the polyethylene surface by staining with crystal violet and changes in the polyethylene surface after the removal of biofilms by densitometric method. The stimulating effect of humic acids of a wide concentration range on the biofilm growth on the polyethylene surface and at the initial stage of its biodegradation has been revealed for the first time. The methodological approaches and the results obtained supplement the information on polyethylene biodegradation and can be applied in biotechnologies.