Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99354, USA.
OSU NMR Facility, Oregon State University, Corvallis, OR, 97331, USA.
Sci Rep. 2018 Jan 16;8(1):813. doi: 10.1038/s41598-017-19119-7.
The degradation and turnover of soil organic matter is an important part of global carbon cycling and of particular importance with respect to attempts to predict the response of ecosystems to global climate change. Thus, it is important to mechanistically understand the processes by which organic matter can be degraded in the soil environment, including contact with reactive or catalytic mineral surfaces. We have characterized the outcome of the interaction of two minerals, birnessite and kaolinite, with two disaccharides, cellobiose and trehalose. These results show that birnessite reacts with and degrades the carbohydrates, while kaolinite does not. The reaction of disaccharides with birnessite produces Mn(II), indicating that degradation of the disaccharides is the result of their oxidation by birnessite. Furthermore, we find that both sugars can inhibit the degradation of a model protein by birnessite, demonstrating that the presence of one organic constituent can impact abiotic degradation of another. Therefore, both the reactivity of the mineral matrix and the presence of certain organic constituents influence the outcomes of abiotic degradation. These results suggest the possibility that microorganisms may be able to control the functionality of exoenzymes through the concomitant excretion of protective organic substances, such as those found in biofilms.
土壤有机质的降解和转化是全球碳循环的重要组成部分，对于预测生态系统对全球气候变化的响应具有特别重要的意义。因此，从机理上理解有机质在土壤环境中可能发生的降解过程非常重要，包括与反应性或催化矿物表面的接触。我们已经描述了两种矿物质（水钠锰矿和高岭石）与两种二糖（纤维二糖和海藻糖）相互作用的结果。这些结果表明，水钠锰矿与碳水化合物发生反应并降解了它们，而高岭石则没有。二糖与水钠锰矿的反应生成了 Mn(II)，这表明二糖的降解是水钠锰矿氧化的结果。此外，我们发现两种糖都可以抑制模型蛋白质被水钠锰矿降解，这表明一种有机成分的存在会影响另一种非生物降解。因此，矿物基质的反应性和某些有机成分的存在都会影响非生物降解的结果。这些结果表明，微生物可能能够通过同时排泄保护性有机物质（如生物膜中发现的物质）来控制外切酶的功能。
