Microplastics, as an emerging pollutant of global importance, have been well documented
in aquatic ecosystems. However, little is known about the effects of microplastics
on agroecosystems, particularly for soil microbial communities. Herein, microplastics
collected from cotton fields in Xinjiang, China, were analysed with a scanning electron
microscope (SEM) and high-throughput sequencing to investigate the attached bacterial
communities. Microplastic surfaces, especially pits and flakes, were colonized by
various microorganisms, suggesting active hydrolysis of plastic debris. The bacterial
communities colonizing microplastics were significantly different in structure from
those in the surrounding soil, plant litter and macroplastics. In addition, statistical
analysis of differentially abundant OTUs showed that microplastics serve as a "special
microbial accumulator" in farmland soil, enriching some taxa that degrade polyethylene,
such as Actinobacteria, Bacteroidetes and Proteobacteria. Co-occurrence network analysis
revealed that the biotic interactions between microorganisms on microplastics are
as complex as those in soil, and Acidobacteria, Chloroflexi, Gemmatimonadetes, and
Bacteroidetes are considered keystone species in bacterial communities. Collectively,
the findings imply that microplastics acted as a distinct habitat for bacteria in
farmland soil, which increases our understanding of microplastic pollution.