[Show abstract][Hide abstract] ABSTRACT: The soil microorganisms at different depths play an important role in soil formation, ecosystem biogeochemistry, recycling of nutrients, and degradation of waste products. The aims of this study were to observe the microbial diversity in the profile of an agricultural soil in northern China, and to research the correlation between soil microbes and geochemistry. First, the soil geochemistry of the profile was investigated through 25 chemical elements. Secondly, the various physiological groups of microorganisms were studied by traditional culture methods. Thirdly, the functional diversity on sole carbon source utilization (SCSU) was evaluated by the BIOLOG system. Finally, the correlation between the soil microbial diversity and geochemistry was analyzed statistically. The results showed that the amounts and proportions of various physiological groups of microorganisms changed with depth. The bacterial functional diversity on SCSU decreased with increasing depth, but evenness of the substrate utilization increased. Although the microbial metabolic diversity was different at every depth, it could be classified into three main groups by principal component analysis and cluster analysis. The various physiological groups of microorganisms showed remarkable correlation with relevant soil chemical elements. The sensitive microbial indicators of soil health were expected to be screened out from actinomyces or ammonifying bacteria.
Journal of Environmental Sciences 02/2008; 20(8):981-8. · 1.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A simple, rapid and cheaper method for direct extraction of DNA from damaged soil where the vegetation was being restored since the 1970s was developed. The soil was difficult to extract DNA from because of low TN (0.162 mg.g -1) and TP (0.227 mg.g -1), but higher humus content (0.469 mg.g -1). The method was based on lysis with a high-salt extraction buffer (0.15 M NaCl, 0.1M Na2EDTA) and extended heating (2h) of the soil suspension in the presence of proteinase K and sodium dodecyl sulfate (SDS). The extraction method required 4h and was tested on the special restoration soil from which DNA extraction is comparatively difficult. Several other methods were tried but failed to yield DNA. This method was much cheaper than commercially available kits. The DNA fragment size in the crude extracts was about 20kb. Crude DNA was purified by improved gel extraction. The results showed that the recovery of DNA from different communities varied greatly. The chemical properties of the soil also showed significant difference among different communities and indicated a great spatial heterogeneity. Spatial heterogeneity could reflect biodiversity. DNA recovery was used as the direct index for biodiversity instead of soil properties. The F-test predicts that the restoration area can and will accommodate high biodiversity.