赤子爱胜蚓对乙草胺污染土壤微生物群落的影响

为研究赤子爱胜蚓对乙草胺污染土壤微生物群落的影响,本实验通过土壤酶测定法、传统平板计数法以及高通量测序法对自然土壤(S)、乙草胺污染土壤(SA)以及蚯蚓处理乙草胺污染土壤(SAE)的微生物群落进行了分析。研究发现,田间推荐使用剂量的乙草胺(5 mg·kg~(-1))使SA中过氧化氢酶、脱氢酶和蔗糖酶的活性下降,但可提高土壤脲酶和碱性磷酸酶的活性,蚯蚓对受乙草胺抑制的土壤酶活性有提升作用,这种促进作用在实验中期最为明显,培养第14 d时蚯蚓处理组(SAE)过氧化氢酶、脱氢酶和蔗糖酶的活性相较于SA处理组分别上升了4%、14%和53%。乙草胺对细菌数量的抑制作用主要发生在实验前期(第3 d),对真菌的抑制作用持续到了整个培养周期结束(30 d)。蚯蚓的加入对细菌和真菌数量的恢复都有一定的促进作用,第3 d和第14 d时SAE中细菌和真菌数量分别增加35%和39%。SAE处理组土壤的pH相较于SA处理组更接近于中性,可溶性有机碳含量更高,这些性质都为土壤微生物提供了适宜的生长环境,从而促进乙草胺污染土壤中微生物数量和活性的恢复。对不同处理土壤的高通量测序结果表明,在门水平上,乙草胺主要使Proteobacteria、Actinobacteria以及Chytridiomycota丰度下降,而使Acidobacteria和Zygomycota丰度上升。蚯蚓能够改善乙草胺污染土壤中的微生物物种组成情况,使其更接近于未污染状态,以上实验结果说明蚯蚓对乙草胺造成的微生物毒害有修复作用。在属水平上,少数微生物比如Sphingomonas、Fusarium、Gaertneriomyces和Pyrenula等能够受到乙草胺刺激而丰度增加,这些微生物可能参与到了乙草胺的微生物降解过程中。

The impact of earthworm (Eisenia fetida)on the microbial community in an acetochlor contaminated soil

In order to investigate the effects of the earthworm (Eisenia fetida)on the microbial community in acetochlor-polluted soil, soil enzyme activity measurement, traditional plate count, and high-throughput sequencing methods were conducted in the present study. Three groups were set up:natural soil (S), soil with acetochlor (SA), and soil with acetochlor and earthworm (SAE). The results showed that 5 mg·kg^-1 of acetochlor (recommended field dosage)decreased catalase, dehydrogenase, and invertase activities; and increased urease and alkaline phosphatase activities. The earthworm restored the catalase, dehydrogenase, and invertase activities by 4%, 14%, and 53%, respectively on the 14^th day of incubation, which was the most obvious period of the earthworm''s effect. The stimulation of the earthworm of bacterial population was transient (the third day of incubation), while its effect on fungi population was long-term (the whole thirty days of incubation). The earthworm repaired the damage to bacterial and fungal populations caused by acetochlor. On day 3 and 14, the bacterial and fungal populations were promoted 35% and 39%, respectively, by the earthworm in the SAE group. The data on soil enzyme activities and microorganism population indicated that the earthworm can repair the ecological damage caused by acetochlor. The soil in the earthworm-containing group (SAE)was characterized as having more neutral pH and higher dissolvable organic carbon content, which provided a more suitable environment for microorganisms. At the phylum level, Proteobacteria, Actinobacteria, and Chytridiomycota were the main phyla inhibited by acetochlor, while Acidobacteria and Zygomycota were stimulated by acetochlor. The earthworm changed the microbial community composition in acetochlor-contaminated soil, making it more similar to that of unspiked soil. The results further illustrate the microbial recovery effect of the earthworm on acetochlor-contaminated soil. At the genus level, a few species like Sphingomonas, Fusarium, Gaertneriomyces, and Pyrenula, promoted by acetochlor, could be the microorganisms involved in acetochlor degradation.