Feld Louise, Hjelmsø Mathis Hjort, Nielsen Morten Schostag, Jacobsen Anne Dorthe, Rønn Regin, Ekelund Flemming, Krogh Paul Henning, Strobel Bjarne Westergaard, Jacobsen Carsten Suhr
Geological Survey of Denmark and Greenland (GEUS), Department of Geochemistry, Copenhagen, Denmark.
University of Copenhagen, Department of Biology, Section of Terrestrial Ecology, Copenhagen, Denmark.
PLoS One. 2015 May 4;10(5):e0126080. doi: 10.1371/journal.pone.0126080. eCollection 2015.
Assessing the effects of pesticide hazards on microbiological processes in the soil is currently based on analyses that provide limited insight into the ongoing processes. This study proposes a more comprehensive approach. The side effects of pesticides may appear as changes in the expression of specific microbial genes or as changes in diversity. To assess the impact of pesticides on gene expression, we focused on the amoA gene, which is involved in ammonia oxidation. We prepared soil microcosms and exposed them to dazomet, mancozeb or no pesticide. We hypothesized that the amount of amoA transcript decreases upon pesticide application, and to test this hypothesis, we used reverse-transcription qPCR. We also hypothesized that bacterial diversity is affected by pesticides. This hypothesis was investigated via 454 sequencing and diversity analysis of the 16S ribosomal RNA and RNA genes, representing the active and total soil bacterial communities, respectively.
Treatment with dazomet reduced both the bacterial and archaeal amoA transcript numbers by more than two log units and produced long-term effects for more than 28 days. Mancozeb also inhibited the numbers of amoA transcripts, but only transiently. The bacterial and archaeal amoA transcripts were both sensitive bioindicators of pesticide side effects. Additionally, the numbers of bacterial amoA transcripts correlated with nitrate production in N-amended microcosms. Dazomet reduced the total bacterial numbers by one log unit, but the population size was restored after twelve days. The diversity of the active soil bacteria also seemed to be re-established after twelve days. However, the total bacterial diversity as reflected in the 16S ribosomal RNA gene sequences was largely dominated by Firmicutes and Proteobacteria at day twelve, likely reflecting a halt in the growth of early opportunists and the re-establishment of a more diverse population. We observed no effects of mancozeb on diversity.
目前评估农药危害对土壤微生物过程的影响所依据的分析方法，对正在进行的过程洞察有限。本研究提出了一种更全面的方法。农药的副作用可能表现为特定微生物基因表达的变化或多样性的变化。为了评估农药对基因表达的影响，我们聚焦于参与氨氧化的amoA基因。我们制备了土壤微观生态系统，并将它们暴露于棉隆、代森锰锌或不施加农药的环境中。我们假设施加农药后amoA转录本的数量会减少，为了验证这一假设，我们使用了逆转录定量聚合酶链反应。我们还假设细菌多样性会受到农药的影响。通过对分别代表活跃和总土壤细菌群落的16S核糖体RNA和RNA基因进行454测序和多样性分析来研究这一假设。
棉隆处理使细菌和古菌的amoA转录本数量减少了两个对数单位以上，并产生了超过28天的长期影响。代森锰锌也抑制了amoA转录本的数量，但只是短暂抑制。细菌和古菌的amoA转录本都是农药副作用的敏感生物指标。此外，在添加氮的微观生态系统中，细菌amoA转录本的数量与硝酸盐产量相关。棉隆使细菌总数减少了一个对数单位，但12天后种群数量恢复。活跃土壤细菌的多样性在12天后似乎也重新建立起来。然而，在第12天，16S核糖体RNA基因序列所反映的总细菌多样性在很大程度上由厚壁菌门和变形菌门主导，这可能反映了早期机会主义者生长的停止以及更多样化种群的重新建立。我们未观察到代森锰锌对多样性有影响。
