Bacterial impact on the wetting properties of soil minerals
Bacterial impact on the wetting properties of soil minerals
复制标题
DOI：
10.1007/s10533-014-0040-9
复制
发表时间：
2015-02-01
期刊：
影响因子：
4
通讯作者：
Kaestner, Matthias
中科院分区：
文献类型：
--
作者：
Achtenhagen, Jan;Goebel, Marc-O.;Kaestner, Matthias
土壤-水分排斥(SWR)是一种被广泛观察且影响严重的现象，但解释SWR发展过程的物理化学框架仍然是一个主要的研究领域。最近的研究表明，微生物量残留物，特别是细胞碎片，对土壤有机质(SOM)的形成有重要影响，并会降低土壤的润湿性。研究还表明，渗透胁迫增加了细菌细胞表面的疏水性。如果微生物是土壤有机质的重要来源，细胞及其残留物在矿物颗粒上的附着会降低矿物的润湿性，在渗透胁迫的情况下这种影响会更加明显。将恶臭假单胞菌的培养物、细胞碎片与矿物质混合，通过测定固体-水接触角(CA)来研究它们对表面润湿性的影响。细菌附着在石英表面导致表面疏水性显著增加(CA增加高达90A)，特别是对受压力的细胞。细胞碎片和胞浆也被发现显著降低了润湿性(高达100安氏度)。这些发现可以解释与SWR相关的各种现象，如临界土壤含水率，也可能是处理后污水灌溉后SWR形成的一个重要解释。研究结果还支持微生物来源SWR的假说，其中大分子生物结构可能比特定类别的有机化合物具有更大的影响。
Soil-water repellency (SWR) is a widely observed phenomenon with severe impacts, but a physicochemical framework to explain the process of SWR development is still a major field of research. Recent studies have shown that microbial biomass residues, in particular cell fragments, contribute significantly to the formation of soil organic matter (SOM) and can decrease wettability. It was also shown that osmotic stress increases the hydrophobicity of bacterial cell surfaces. If microorganisms are an important source of SOM, the attachment of cells and their residues on mineral grains should decrease wettability of minerals, and the effect should be more pronounced in case of osmotic stress. Cultures of Pseudomonas putida, either unstressed or exposed to osmotic stress, and cell fragments were mixed with minerals and the impact on surface wetting properties was investigated by determining the solid-water contact angle (CA). Attachment of bacteria to quartz surfaces resulted in a significant increase in hydrophobicity of the surfaces (CA increase by up to 90A degrees), in particular for stressed cells. Cell fragments and cytosol were also found to decrease wettability significantly (CAs of up to 100A degrees). These findings may explain various phenomena related to SWR, like critical soil-water content, and may be one important explanation for the formation of SWR after irrigation with treated sewage effluents. The results also support the hypothesis of a microbial origin of SWR, in which macromolecular biological structures may have a greater impact than specific classes of organic compounds.