Soils can be contaminated with substances arising from anthropogenic sources, but also with natural bioactive compounds produced by plants, such as terpenes and flavonoids. While terpenes and flavonoids have received much less attention from research studies than metals, the effects that phytocompounds can have on soil organisms such as beneficial microorganisms should not be neglected. Herein we report the sole and combined exposure of Rhizobium to cadmium, to the monoterpene alpha-pinene and to the flavanol quercetin. A range of environmentally relevant concentrations of the phytocompounds was tested. Physiological (growth, protein content and intracellular Cd concentration), oxidative damage (lipid peroxidation, protein carbonylation) and antioxidant mechanisms (superoxide dismutase, catalase, glutathione, glutathione-S-transferases, protein electrophoretic profiles) were assessed. Results suggest that exposure to both phytocompounds do not influence Rhizobium growth, but for combined exposure to phytocompounds and Cd, different responses are observed. At low concentrations, phytocompounds seem to relieve the stress imposed by Cd by increasing antioxidant responses, but at high concentrations this advantage is lost and membrane damage may even be exacerbated. Thus, the presence of bioactive phytocompounds in soil may influence the tolerance of microorganisms to persistent toxicants, and may change their impact on the environment.

中文翻译：

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根瘤菌对单一和联合暴露于镉和植物化合物α-pine烯和槲皮素的反应。

土壤可能被人为来源的物质污染，但也可能被植物产生的天然生物活性化合物（如萜烯和类黄酮）污染。尽管萜烯和类黄酮比金属引起的关注要少得多，但植物化合物对土壤生物（如有益微生物）的影响却不容忽视。在此，我们报告了根瘤菌对镉，单萜α-pine烯和黄烷醇槲皮素的唯一和联合暴露。测试了一系列与环境有关的植物化合物浓度。生理（生长，蛋白质含量和细胞内Cd浓度），氧化损伤（脂质过氧化，蛋白质羰基化）和抗氧化机制（超氧化物歧化酶，过氧化氢酶，谷胱甘肽，谷胱甘肽S-转移酶，蛋白质电泳图谱）进行了评估。结果表明，暴露于两种植物化合物均不会影响根瘤菌的生长，但是如果将其暴露于植物化合物和Cd，则观察到不同的响应。在低浓度下，植物化合物似乎可以通过增加抗氧化剂的反应来缓解Cd施加的压力，但是在高浓度下，这种优势会丧失，甚至可能加剧膜的破坏。因此，土壤中生物活性植物化合物的存在可能影响微生物对持久性毒物的耐受性，并可能改变其对环境的影响。植物化合物似乎可以通过增加抗氧化剂的反应来减轻Cd施加的压力，但是在高浓度下，这种优势就会丧失，甚至会加剧膜的破坏。因此，土壤中生物活性植物化合物的存在可能影响微生物对持久性毒物的耐受性，并可能改变其对环境的影响。植物化合物似乎可以通过增加抗氧化剂的反应来减轻Cd施加的压力，但是在高浓度下，这种优势会丧失，甚至可能加剧膜的损害。因此，土壤中生物活性植物化合物的存在可能影响微生物对持久性毒物的耐受性，并可能改变其对环境的影响。