Department of Agronomy, University of Maryland, College Park, Maryland 20742, and Nitrogen Fixation and Soybean Genetics Laboratory, U.S. Department of Agriculture, Agricultural Research Station, Beltsville, Maryland 20705.
Appl Environ Microbiol. 1987 Feb;53(2):315-9. doi: 10.1128/aem.53.2.315-319.1987.
The application of sewage sludge to land may increase the concentration of heavy metals in soil. Of considerable concern is the effect of heavy metals on soil microorganisms, especially those involved in the biocycling of elements important to soil productivity. Bradyrhizobium japonicum is a soil bacterium involved in symbiotic nitrogen fixation with Glycine max, the common soybean. To examine the effect of metal-rich sludge application on B. japonicum, the MICs for Pb, Cu, Al, Fe, Ni, Zn, Cd, and Hg were determined in minimal media by using laboratory reference strains representing 11 common serogroups of B. japonicum. Marked differences were found among the B. japonicum strains for sensitivity to Cu, Cd, Zn, and Ni. Strain USDA 123 was most sensitive to these metals, whereas strain USDA 122 was most resistant. In field studies, a silt loam soil amended 11 years ago with 0, 56, or 112 Mg of digested sludge per ha was examined for total numbers of B. japonicum by using the most probable number method. Nodule isolates from soybean nodules grown on this soil were serologically typed, and their metal sensitivity was determined. The number of soybean rhizobia in the sludge-amended soils was found to increase with increasing rates of sludge. Soybean rhizobia strains from 11 serogroups were identified in the soils; however, no differences in serogroup distribution or proportion of resistant strains were found between the soils. Thus, the application of heavy metal-containing sewage sludge did not have a long-term detrimental effect on soil rhizobial numbers, nor did it result in a shift in nodule serogroup distribution.
将污水污泥施用于土地可能会增加土壤中重金属的浓度。重金属对土壤微生物的影响尤其令人关注，特别是对那些参与对土壤生产力至关重要的元素生物循环的微生物。根瘤菌（Bradyrhizobium japonicum）是一种与大豆（Glycine max）共生固氮的土壤细菌。为了研究富含金属的污泥施用于根瘤菌的影响，使用代表根瘤菌 11 个常见血清群的实验室参考菌株，在最小培养基中确定了 Pb、Cu、Al、Fe、Ni、Zn、Cd 和 Hg 的 MIC。根瘤菌菌株对 Cu、Cd、Zn 和 Ni 的敏感性存在明显差异。菌株 USDA 123 对这些金属最敏感，而菌株 USDA 122 最具抗性。在田间研究中，对 11 年前施用量为 0、56 或 112 Mg 消化污泥/公顷的粉壤土进行了研究，采用最可能数法（most probable number method）检测根瘤菌的总数。从在该土壤上生长的大豆根瘤中分离出的根瘤菌进行血清分型，并确定其金属敏感性。发现污泥施用量增加会导致土壤中根瘤菌数量增加。在土壤中鉴定出了来自 11 个血清群的大豆根瘤菌菌株；然而，在土壤之间未发现血清群分布或抗性菌株比例的差异。因此，重金属含量污水污泥的施用对土壤根瘤菌数量没有长期的不利影响，也没有导致根瘤菌血清群分布的变化。
