Nguyen-Viet H, Gilbert D, Mitchell E A D, Badot P-M, Bernard N
Laboratory of Environmental Biology, USC INRA, EA 3184, University of Franche-Comté, Place Leclerc 25030, Besançon, France.
Microb Ecol. 2007 Aug;54(2):232-41. doi: 10.1007/s00248-006-9192-z. Epub 2007 Mar 8.
Ecotoxicological studies usually focus on single microbial species under controlled conditions. As a result, little is known about the responses of different microbial functional groups or individual species to stresses. In an aim to assess the response of complex microbial communities to pollution in their natural habitat, we studied the effect of a simulated lead pollution on the microbial community (bacteria, cyanobacteria, protists, fungi, and micrometazoa) living on Sphagnum fallax. Mosses were grown in the laboratory with 0 (control), 625, and 2,500 microg L(-1) of Pb(2+) diluted in a standard nutrient solution and were sampled after 0, 6, 12, and 20 weeks. The biomasses of bacteria, microalgae, testate amoebae, and ciliates were dramatically and significantly decreased in both Pb addition treatments after 6, 12, and 20 weeks in comparison with the control. The biomass of cyanobacteria declined after 6 and 12 weeks in the highest Pb treatment. The biomasses of fungi, rotifers, and nematodes decreased along the duration of the experiment but were not significantly affected by lead addition. Consequently, the total microbial biomass was lower for both Pb addition treatments after 12 and 20 weeks than in the controls. The community structure was strongly modified due to changes in the densities of testate amoebae and ciliates, whereas the relative contribution of bacteria to the microbial biomass was stable. Differences in responses among the microbial groups suggest changes in the trophic links among them. The correlation between the biomass of bacteria and that of ciliates or testate amoebae increased with increasing Pb loading. We interpret this result as an effect on the grazing pathways of these predators and by the Pb effect on other potential prey (i.e., smaller protists). The community approach used here complements classical ecotoxicological studies by providing clues to the complex effect of pollutant-affecting organisms both directly and indirectly through trophic effects and could potentially find applications for pollution monitoring.
生态毒理学研究通常聚焦于在受控条件下的单一微生物物种。因此，对于不同微生物功能组或单个物种对应激的反应了解甚少。为了评估复杂微生物群落对其自然栖息地污染的反应，我们研究了模拟铅污染对生长在泥炭藓上的微生物群落（细菌、蓝细菌、原生生物、真菌和微型后生动物）的影响。苔藓在实验室中用标准营养液稀释的0（对照）、625和2500微克/升的Pb²⁺培养，并在0、6、12和20周后取样。与对照相比，在添加铅的两种处理中，细菌、微藻、有壳变形虫和纤毛虫的生物量在6、12和20周后均显著大幅下降。在最高铅处理中，蓝细菌的生物量在6和12周后下降。真菌、轮虫和线虫的生物量在实验过程中减少，但未受到铅添加的显著影响。因此，在12和20周后，两种添加铅处理的总微生物生物量均低于对照。由于有壳变形虫和纤毛虫密度的变化，群落结构发生了强烈改变，而细菌对微生物生物量的相对贡献保持稳定。微生物组之间反应的差异表明它们之间营养联系的变化。细菌生物量与纤毛虫或有壳变形虫生物量之间的相关性随铅负荷增加而增加。我们将这一结果解释为铅对这些捕食者的捕食途径以及对其他潜在猎物（即较小的原生生物）的影响。这里使用的群落方法通过提供污染物通过营养效应直接和间接影响生物体的复杂效应线索，补充了经典的生态毒理学研究，并可能在污染监测中找到应用。
