Measuring the soil-microbial interface: extraction of extracellular polymeric substances (EPS) from soil biofilms
Measuring the soil-microbial interface: extraction of extracellular polymeric substances (EPS) from soil biofilms
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DOI：
10.1016/j.soilbio.2014.01.025
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发表时间：
2014-05
影响因子：
9.7
通讯作者：
Marc Redmile-Gordon;P. Brookes;R. Evershed;K. Goulding;P. Hirsch
中科院分区：
文献类型：
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作者：
Marc Redmile-Gordon;P. Brookes;R. Evershed;K. Goulding;P. Hirsch
许多土壤微生物存在于生物膜中。这些生物膜的典型特征是可变量的胞外聚合物物质（EPS：主要是多糖，糖缀合物和蛋白质）和嵌入的微生物细胞。尚未描述测量土壤-EPS（排除微生物细胞的生物膜）的方法。本工作探讨了五种提取方法估计土壤EPS含量变化的潜力。通过向湿润土壤中的微生物生物量提供不稳定的C（甘油），然后施加干燥胁迫，在原位培养EPS。五种提取方法中只有两种显示出响应于底物添加的多糖产量的统计学显著增加。腐殖化的有机物质，估计其腐殖酸当量（HAE）被用来指示的程度的细胞外污染，和/或创建的腐殖文物-这两者都影响检测的变化EPS。当应用设计用于提取球囊霉素相关土壤蛋白（GRSP）的原始方法和改进方法时，HAE浓度非常高。提取方法，包括加热稀硫酸似乎高估了EPS-多糖。使用微生物ATP作为细胞裂解的指标，置信度只能归因于阳离子交换树脂提取的EPS。使用该方法，EPS-多糖的预期增加是明显的。EPS提取物的HAE/蛋白质比率在阳离子交换的情况下也是最低的-表明该方法不会引起来自腐殖化土壤有机物质的过度污染或产生相关的伪影。
Many soil microbes exist in biofilms. These biofilms are typified by variable quantities of extracellular polymeric substances (EPS: predominantly polysaccharides, glycoconjugates, and proteins) and the embedded microbial cells. A method to measure soil-EPS (the biofilm exclusive of microbial cells) has not yet been described. The present work investigates the potential of five extraction methods to estimate changes in soil-EPS content. A rationale for selection of appropriate EPS extraction and methodology is discussed, including the crucial consideration of both intracellular and extracellular contamination.EPS was developedin situby provision of labile C (glycerol) to the microbial biomass of a moist soil and then applying desiccation stress. Only two out of the five extraction methods showed statistically significant increases in polysaccharide production responding to substrate addition. Humified organic matter, estimated by its humic acid equivalent (HAE) was used to indicate the degree of extracellular contamination, and/or creation of humic artefacts – both of which affect detection of changes in EPS. The HAE concentration was very high when applying original and modified methods designed to extract glomalin related soil protein (GRSP). Extraction methods involving heating with dilute sulphuric acid appeared to overestimate EPS-polysaccharide. Using microbial ATP as an indicator of cell-lysis, confidence could only be ascribed to EPS extraction with cation exchange resin. Using this method, the expected increases in EPS-polysaccharide were clearly apparent. The HAE/protein ratios of EPS extracts were also lowest with cation exchange – indicating this method did not cause excessive contamination from humified soil organic matter or create related artefacts.