Effects of different colored polyethylene mulching films on bacterial communities from soil during enrichment incubation

Studies have shown that mulching agricultural fields with plastic residues can influence microbial communities in the environment, but few studies have investigated the differences in the soil microbial communities in distinct areas under mulching with different colored plastic products. Thus, in this study, we explored how different colored polyethylene mulching films (PMFs) might affect soil bacterial communities during enrichment incubation. We found significant differences in the bacterial communities under different colored PMFs after incubation. Treatment with the same colored PMF obtained more similar bacterial community compositions. For instance, at the class level, Gammaproteobacteria and Bacteroidia were most abundant with black PMF, whereas Actinobacteria and Bacteroidia were most abundant with white PMF. The most abundant genera were Acinetobacter and Chryseobacterium with black PMF but Rhodanobacter and Paenarthrobacter with white PMF. Polyethylene- and hydrocarbon-degrading bacteria were the core members detected under both treatments, and the bacterial communities were predicted to have the potential for the biodegradation and metabolism of xenobiotics after enrichment culture according to the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) tool. In addition, the bacterial communities in soil from Xinjiang treated with white PMF and in soil from Yangling treated with black PMF were strongly correlated and stable. Our results suggest that the color of the PMF applied affected the soil bacterial communities, where plastics with the same color may have recruited similar species of microorganisms, although the origins of these microorganisms were not the same.

Community structure and functional diversity of the plastisphere in aquaculture waters: Does plastic color matter?

Microplastics (MPs) serve as a niche for colonization of biofilm-forming microorganisms, termed as plastisphere. Distinct microbial assemblages between MPs and surrounding waters have been well reported, but little is known about driving factors affecting biofilm development on plastic surfaces. Here, to investigate the influence of plastic colors on microbial assemblages, we performed a biofilm incubation experiment, in an aquaculture pond, using MPs in colors (blue, yellow and transparent) that commonly found in the aquatic environments for 30 days. We examined the community structure and function of plastisphere by using 16S rRNA sequencing. The results showed that plastisphere communities exhibited a higher diversity and evenness compared with the water community. MPs especially the blue MPs had more unique species, which might indicate a plastic color/additive-driven selection of microorganisms on MPs. A significant distinctness in bacterial community composition between MPs and the water was found, mainly caused by large amounts of Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium but trace amounts of Microcystis_PCC-7914 on MPs. Due primarily to rich in Aquabacterium but lack of norank_f__norank_o__1-20 on blue MPs than on transparent and yellow MPs, a clear separation between plastisphere communities of three colors of MPs was also observed. Moreover, compared with the water column, the metabolic pathways, e.g., transport and metabolism of amino acid, carbohydrate and inorganic ion, on plastisphere especially those of blue MPs were generally enriched. Biofilms colonizing on blue MPs appeared to have a higher functional diversity than those on transparent or yellow MPs. These results might suggest that plastic colors have impacts on the community structure and functional diversity of plastisphere.