微塑料对外生菌根真菌生长和抗氧化系统的影响

土壤中的微塑料污染及其毒理学效应已逐渐引起广泛关注,但微塑料对外生菌根真菌的毒性研究仍不多见。为此,以彩色豆马勃(Pisolithus tinctorius,Pt)和松乳菇(Lactarius delicious,Ld)作为供试菌株,选用粒径80 nm和4 μm的单分散聚苯乙烯塑料微球(PS-MPs)作为试验材料,采用固体平板法和液体培养法研究不同粒径不同质量浓度(10~300 mg·L^-1)的PS-MPs对外生菌根真菌生长情况、丙二醛(MDA)含量、可溶性蛋白含量、抗氧化酶活性、组织电导率等指标的影响。结果显示,高浓度(200~300 mg·L^-1)的PS-MPs显著(P<0.05)抑制2株真菌的生长,且粒径4 μm的PS-MPs较粒径80 nm的对两株真菌的生物量表现出更强的抑制作用。随PS-MPs质量浓度的升高,Pt和Ld的超氧化物歧化酶活性始终显著(P<0.05)高于对照,且表现出先升高后降低的趋势。当暴露于2种粒径的PS-MPs之中时,Pt和Ld的过氧化氢酶活性均在300 mg·L^-1处理下最低,且显著(P<0.05)低于对照;而过氧化物酶活性在各处理下均显著(P<0.05)高于对照。与对照相比,PS-MPs处理下,Pt和Ld的MDA含量显著(P<0.05)升高(除10 mg·L^-1 4 μm PS-MPs处理下的Pt和200 mg·L^-1 4 μm PS-MPs处理下的Ld外),可溶性蛋白含量显著(P<0.05)降低(除10、20 mg·L^-1 80 nm PS-MPs处理下的Pt和10 mg·L^-1 80 nm PS-MPs处理下的Ld外),菌丝组织电导率显著(P<0.05)升高。据此推测,PS-MPs对外生菌根真菌的影响机制可能涉及氧化应激反应,且不同菌株对不同粒径PS-MPs的响应不同。研究结果可为揭示微塑料对土壤外生菌根真菌的急性毒性提供依据。

Effects of microplastics on growth and antioxidant system of ectomycorrhizal fungi

Microplastics pollution in soil and its toxicological effects have gradually attracted wide attention, but the toxicity of microplastics to ectomycorrhizal fungi (ECMF) is not clear yet. Therefore, Pisolithus tinctorius(Pt) and Lactarius delicius(Ld) were used as test strains in the present study, and monodisperse polystyrene microspheres (PS-MPs) with particle sizes of 80 nm and 4 μm were used as experimental materials. The effects of PS-MPs with different particle sizes and different concentrations (10-300 mg·L^-1) on the growth, malondialdehyde (MDA) content, soluble protein content, antioxidant enzymes activities and tissue conductivity of ECMF were explored by solid plate method and liquid culture method. The results showed that 200-300 mg·L^-1 PS-MPs significantly (P<0.05) inhibited the growth of Pt and Ld, and the PS-MPs with particle size of 4 μm showed stronger inhibition effect than PS-MPs with particle size of 80 nm. With the elevated concentration of PS-MPs, the superoxide dismutase activities of Pt and Ld exhibited an increasing first and then decreasing trend, and were all significantly (P<0.05) higher than that of control. When exposed to PS-MPs with different particle sizes, the catalase activity reached the lowest point under 300 mg·L^-1 PS-MPs treatment for Pt and Ld, and was significantly (P<0.05) lower than that of the control, while peroxidase activity was significantly (P<0.05) higher than that of control under all treatments. Besides, compared with the control, MDA content of Pt and Ld was significantly (P<0.05) elevated under other treatments (excluding Pt under 10 mg·L^-1 4 μm PS-MPs and Ld under 200 mg·L^-1 4 μm PS-MPs), soluble protein content was significantly (P<0.05) decreased (excluding Pt under 10, 20 mg·L^-1 80 nm PS-MPs and Ld under 10 mg·L^-1 80 nm PS-MPs), and the electrical conductivity of mycelium tissue was significantly (P<0.05) increased. Thus, it was inferred that the influence mechanism of PS-MPs on ECMF may involve oxidative stress, and different strains have different responses to PS-MPs with different particle sizes. These results would provide basis for the study regarding acute toxicity of microplastics on soil ECMF.