EFFECTS OF MICROPLASTICS ON MICROBIAL COMMUNITIES AND FUNCTIONAL GENES IN SOIL WITH DIFFERENT AGGREGATE-FRACTION LEVELS
As a new type of environmental pollutant,microplastics pose a serious threat to the soil ecosystem.Studying the effects of microplastics on soil microorganisms and their functions plays an important role in understanding the harm of microplastic pollution to terrestrial ecosystems.Based on the theory of soil heterogeneity,combining soil physical grouping methods and llumina Miseq high-throughput sequencing technology,this paper analyzed the effect of microplastics on soil microorganisms and their functions in soil with different aggregate-fraction levels.The results showed that microplastics altered the soil microbial community structure by significantly increasing and decreasing the abundance of Actinobacteria and Proteobacteria,respectively.Actinobacteria replaced Proteobacteria as the dominant phylum.Furthermore,the relative abundance levels of pathways related to carbohydrate metabolism,lipid metabolism,xenobiotics biodegradation and metabolism,metabolism of terpenoids and polyketides,and immune disease in microplastic treatments were higher than those in control treatments.The direction of effect of microplastics on bacterial metabolic function was consistent in three aggregate-size fractions,but the degree of effect decreased by the sequence of coarse particulate fraction(0.25 to 2 mm),non-aggregated silt and clay fraction(<0.053 mm)and micro-aggregate fraction(0.053 to 0.25 mm).Among three aggregate-size fractions,specific genes involved in labile-C degradation,recalcitrant-C degradation,organic N conversion,denitrification,and organic P mineralization were significantly enriched in microplastic treatments.The results showed that microplastic could change microbial community structure and function,which might change the ecological function of soil.