Shen J, Bartha R
Department of Biochemistry and Microbiology, Cook College, Rutgers University, New Brunswick, New Jersey 08903-0231, USA.
Appl Environ Microbiol. 1996 Jul;62(7):2411-5. doi: 10.1128/aem.62.7.2411-2415.1996.
Biodegradability screening tests of soil commonly measure 14CO2 evolution from radiolabeled test compounds, and glucose has often served as a positive control. When constant amounts of radiolabel were added to soil in combination with increasing amounts of unlabeled substrates, glucose and some related hexoses behaved in an anomalous manner. In contrast to that of formate, benzoate, n-hexadecane, or bis(2-ethylhexyl) phthalate, dilution of glucose radiocarbon with unlabeled glucose increased rather than decreased the rate and extent of 14CO2 evolution. [14C]glucose incorporation into biomass and Vmax values were consistent with the interpretation that application of relatively high concentrations of glucose to soil shifts the balance of the soil microbial community from the autochthonous (humus-degrading) to the zymogeneous (opportunistic) segment. The higher growth and turnover rates that define zymogeneous microorganisms, combined with a lower level of carbon incorporation into their biomass, result in the evolution of disproportionate percentages of 14CO2. When used as positive controls, glucose and related hexoses may raise the expectations for percent 14CO2 evolution to levels that are not realistic for other biodegradable compounds.
土壤的生物降解性筛选试验通常测量放射性标记测试化合物产生的14CO2，葡萄糖常作为阳性对照。当向土壤中添加恒定数量的放射性标记物，并同时增加未标记底物的量时，葡萄糖和一些相关己糖的表现异常。与甲酸盐、苯甲酸盐、正十六烷或邻苯二甲酸二（2-乙基己基）酯不同，用未标记的葡萄糖稀释葡萄糖放射性碳会增加而非降低14CO2的释放速率和程度。[14C]葡萄糖掺入生物量和Vmax值与以下解释一致：向土壤中施用相对高浓度的葡萄糖会使土壤微生物群落的平衡从原生（腐殖质降解）部分转向发酵性（机会性）部分。定义发酵性微生物的较高生长和周转速率，再加上其生物量中较低的碳掺入水平，导致释放出不成比例的14CO2百分比。当用作阳性对照时，葡萄糖和相关己糖可能会将14CO2释放百分比的预期提高到其他可生物降解化合物不现实的水平。
