典型氧化还原环境中微塑料表面的微生物群落组成特征与构建机制

微塑料广泛分布在微生物驱动的生物地球化学循环中，其表面会富集独特特征的微生物群落，构成微塑料圈（plastisphere）.自然环境中广泛存在的多种氧化还原环境不仅会影响微塑料圈中微生物群落的组成，还会影响微塑料的最终归宿.为探究典型氧化还原环境中微塑料表面的微生物群落组成特征与构建机制，将3种微塑料PHA （聚羟基脂肪酸酯）、PLA （聚乳酸）和PVC （聚氯乙烯）放置于好氧、硝酸盐还原、铁氧化物还原、硫酸盐还原和产甲烷这5种典型氧化还原环境中，利用污泥作为接种物，进行微宇宙模拟培养实验.结果表明，在分类学和系统发育学上，微塑料因子分别影响了微塑料表面18.94%和46.67%的微生物群落，氧化还原环境因子分别影响了微塑料表面31.04%和90.00%的微生物群落.与污泥相比较，3种微塑料表面富集的微生物群落丰富度和均匀度均降低，其中降低最明显的是更易降解的PHA微塑料，而难降解的PLA和PVC微塑料表面的微生物群落变化特征相似.PHA微塑料表面富集的微生物中，Anaerocolumna（26.44%）为其优势菌种，较少富集与氧化还原反应相关的特征菌群；PLA和PVC中，Clostridium_sensu_stricto_7 （15.49%和11.87%）为其优势菌种，且显著富集与氧化还原反应相关的特征菌群，表明与氧化还原反应相关的特征菌群更易于富集在难降解的微塑料表面，进而可能对生物地球化学循环速率造成影响.

Composition Characteristics and Construction Mechanism of Microbial Community on Microplastic Surface in Typical Redox Environments

Microplastics are widely distributed in the biogeochemical cycle driven by microbes. Their surface is enriched with unique microbial communities, called plastispheres. Various redox environments that exist widely in the natural environment can affect the microbial composition in the plastisphere and the fate of the microplastics. To explore the microbial community composition and construction mechanism on the surface of microplastics in typical redox environments, three microplastics, PHA (polyhydroxyalkanoates), PLA (polylactic acid), and PVC (polyvinyl chloride), were placed in five specific redox environments:aerobic, nitrate reduction, iron oxide reduction, sulfate reduction, and methane production. The culture experiment simulated the microcosm, which was inoculum by sludge. The results showed that microplastic factors affected 18.94% and 46.67% of the microbial communities on the plastisphere in taxonomy and phylogeny, respectively. Redox factors affected 31.04% and 90.00% of the microbial communities on the plastisphere in taxonomy and phylogeny, respectively. Compared with that in sludge, the microbial community richness and diversity were reduced on the three microplastics. The most apparent reduction was found on the plastisphere of more degradable PHA. At the same time, microbial communities on the refractory PLA and PVC surfaces remained similar. Anaerocolumna (26.44%) was the dominant genus on the surface of PHA microplastics, whereas microbes related to the redox reaction were less enriched. Clostridium_sensu_stricto_7 (15.49% and 11.87%) was the dominant strain on PLA and PVC microplastics, and the microbes related to the redox reaction were significantly enriched. Thus, characteristic microbes involved in the redox reaction will be enriched in the surface of refractory microplastics, and microplastics may affect the rate of biogeochemical cycling.