海岸环境中两类软质微塑料表面生物膜DNA的提取方法比较与优化

微塑料因粒径小、比表面积大，可作为重金属、有机污染物以及病原微生物的载体。已有研究表明，微塑料表面附着的微生物主要以生物膜的形式存在。本研究以山东省海岸带环境中常见的两类软质塑料——发泡类聚苯乙烯（expanded polystyrene，EPS）和聚乙烯薄膜（polyethylene films，PE）为研究对象，比较了MP FastDNA®和MOBIO PowerSoil®两种DNA提取试剂盒对微塑料表面生物膜DNA的提取效果，探讨了不同的微塑料粒径和数量对DNA提取效果的影响。结果表明，MP FastDNA®试剂盒对两种软质微塑料表面生物膜DNA的提取浓度显著低于MOBIO PowerSoil®试剂盒（1.0~12.5倍）。采用MP FastDNA®试剂盒提取的PE表面DNA的浓度约为EPS的1.3~4.4倍。当微塑料数量不大于20片时，小粒径（1~3 mm）的EPS表面生物膜DNA浓度显著高于大粒径（3~5 mm） EPS，而对于PE薄膜则相反。对于两种粒径的EPS，微塑料表面DNA浓度均随着微塑料数量的增加而显著增加，但对于小粒径（1~3 mm）的PE薄膜，DNA浓度随微塑料数量的增加呈先增后减的趋势；而大粒径（3~5 mm）的PE薄膜表面DNA浓度随微塑料数量的增加而降低。微塑料的粒径和数量对其表面DNA提取效果影响的差异与微塑料的类型及其理化性质有关。本研究可为海洋与海岸环境中微塑料表面微生物群落组成与多样性研究提供方法支撑。

Comparison and optimization of biofilm DNA extraction from two types of soft microplastics in the coastal environment

Microplastics could serve as carriers for heavy metals, organic pollutants and pathogens in the coastal and marine environment due to their small sizes and large specific surface area. It has been reported that the microbial colonizers attaching on the surface of microplasti cs mainly assemblaged in the form of biofilms. In this study, two types of soft microplastics, expanded polystyrene (EPS) and polyethylene films (PE), were selected as tested microplastics that were commonly found in the coastal environment in Shandong province. Two DNA extraction kits (MP FastDNA^® and MOBIO PowerSoil^®) were used to compare their DNA extraction efficiency from different microplastic biofilms. Moreover, impacts from different particle sizes and quantities on DNA extraction efficiency of microplastic-associated biofilms were also evaluated. The results showed that concentrations of biofilm DNA extracted by FastDNA^® kit were significantly higher than by MOBIO PowerSoil^®kit (1.0-12.5 times). DNA concentrations from PE biofilm were about 1.3-4.4 times higher than that from EPS extracted by FastDNA^®. When the quantities of microplastics were no more than 20, DNA concentrations from small sizes (1-3 mm) EPS were significantly lower than that from large sizes (3-5 mm), while it was totally in opposition for PE. With the increasing of microplastics quantities, DNA concentrations were significantly increased in both two sizes of EPS. But for small sizes (1-3 mm) of PE, DNA concentration showed an increasing initially and decreasing afterward trend with the increasing of PE quantities. However, for large sizes (3-5 mm) of PE, DNA concentrations were decreasing with the increasing of PE quantities. Different impacts of microplastic sizes and quantities on DNA concentrations could be attributed to the types and physicochemical properties of microplastics. Results from this study will be helpful for providing methodological support for the research of microbial community composition and diversity of microplastic-associated biofilms in the coastal and marine environment.