IS THE DEHYDROGENASE ASSAY INVALID AS A METHOD TO ESTIMATE MICROBIAL ACTIVITY IN COPPER-CONTAMINATED SOILS
IS THE DEHYDROGENASE ASSAY INVALID AS A METHOD TO ESTIMATE MICROBIAL ACTIVITY IN COPPER-CONTAMINATED SOILS
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DOI：
10.1016/0038-0717(91)90170-o
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发表时间：
1991-01-01
影响因子：
9.7
通讯作者：
BROOKES, PC
中科院分区：
文献类型：
--
作者：
CHANDER, K;BROOKES, PC
土壤脱氢酶活性通常通过氯化三苯基四唑（TTC）转化为三苯基甲（TPF）来估计。有许多报道，在铜污染的土壤中或在最近修订的铜污染的污水污泥的土壤中，脱氢酶活性比其他指标的微生物活性更大的比例下降。我们描述了四个实验，测量铜的脱氢酶测定的影响。在第一，土壤微生物生物量，土壤脱氢酶活性和生物量比脱氢酶活性进行了比较，在土壤中污染的重金属，包括铜，和在未污染的土壤。重金属污染土壤中的生物量比脱氢酶活性比未污染土壤中的生物量低约35%。相比之下，以前的工作表明，生物量比呼吸速率约快1.5倍，在金属污染的土壤。在第二个实验中，将污水污泥（未污染的，被Cu、Ni、Cd或Zn单独污染的，以及含有这些金属组合的污泥）分别添加到未污染的土壤中，并在25 ℃下培养7天。大，类似的增加，生物量碳，CO2的演变和生物量比呼吸测量内所有污泥修正的土壤在1和7天后，污泥添加。土壤脱氢酶活性增加类似的污泥，其中不含添加铜修改的土壤。因此，在所有这些处理中，生物量的比脱氢酶活性非常相似。与此相反，土壤脱氢酶活性和比脱氢酶活性的生物量与富铜污泥或污泥含有所有的金属，包括铜，是2 - 3倍，小于在其他处理。在第三个实验中，TPF孵育单独的解决方案（0 - 100毫克l-1）的重金属在土壤的情况下。TPF的吸光度几乎不受影响，在任何浓度的镍，镉或锌，但下降到几乎为零之间0和20毫克铜l-1。如果这种非生物反应发生在土壤中，它将被错误地报告为脱氢酶活性降低。在第四个实验中，通过将TPF添加到先前与各种富含金属的污泥一起孵育的土壤中来测试这一点。由于TPF的吸光度显着降低，在含有富铜污泥的土壤，但在其他处理不受影响。因此，铜污染土壤脱氢酶活性明显降低的主要原因是TPF与铜之间的非生物反应。以往关于铜对土壤脱氢酶活性影响的研究没有考虑这一现象，因此，许多研究可能是无效的。
Soil dehydrogenase activity is commonly estimated from the conversion of triphenyltetrazolium chloride (TTC) to triphenylformazan (TPF). There are many reports of larger proportional decreases in dehydrogenase activity than in other indices of microbial activity in Cu-contaminated soils or in soils recently amended with Cu-contaminated sewage sludge. We describe four experiments which measured the effects of Cu on the dehydrogenase assay. In the first, soil microbial biomass, soil dehydrogenase activity and biomass specific dehydrogenase activity were compared in a soil contaminated with heavy metals, including Cu, and in an uncontaminated soil. The specific dehydrogenase activity of the biomass was about 35% less in the metal-contaminated soil than in the uncontaminated soil. In contrast, previous work showed that the biomass specific respiration rate was about 1.5 times faster in the metal-contaminated soil. In the second experiment, sewage sludges (uncontaminated, contaminated singly with Cu, Ni, Cd or Zn and a sludge containing the metals in combination) were added separately to an uncontaminated soil and incubated for 7 days at 25-degrees-C. Large, similar increases in biomass C, CO2 evolution and biomass specific respiration were measured within all sludge-amended soils at 1 and 7 days after sludge addition. Soil dehydrogenase activity increased similarly in the soils amended with sludges which contained no added Cu. Thus the specific dehydrogenase activity of the biomass was very similar in all these treatments. In contrast, soil dehydrogenase activity and specific dehydrogenase activity of the biomass in the soils amended with Cu-rich sludge or with the sludge containing all the metals, including Cu, were 2-3 times smaller than in the other treatments. In the third experiment, TPF was incubated with separate solutions (0-100 mg l-1) of heavy metals in the absence of soil. Absorbance of TPF was virtually unaffected at any concentration of Ni, Cd or Zn but declined almost to zero between 0 and 20 mg Cu l-1. If this abiological reaction occurred in soil it would be reported, incorrectly, as decreased dehydrogenase activity. This was tested in the fourth experiment by adding TPF to soils previously incubated with the various metal-rich sludges. Absorbance due to TPF was significantly decreased in the soils containing Cu-rich sludges, but was unaffected in the other treatments. It thus appears that the main reason why soils contaminated with Cu apparently have significantly decreased dehydrogenase activities is the abiological reaction between TPF and Cu. Previous research on the effects of Cu on soil dehydrogenase activity has not considered this phenomenon and much of it, therefore, is probably invalid.