黄土高原石油污染土壤微生物群落结构及其代谢特征

针对污染胁迫下土壤微生物群落变化和代谢变异等问题,基于平板稀释法和Biolog微平板分析方法,研究了陕北黄土高原石油污染土壤微生物群落结构、代谢特征及其功能多样性。结果表明,不同类群的土壤微生物对石油污染胁迫的响应不同,污染土壤细菌和真菌数量高出清洁土壤1个数量级,而污染土壤的放线菌数量极显著减少(P0.01);污染土壤和清洁土壤微生物对糖类和多聚物类碳源较易利用,污染土壤微生物总体上代谢碳源的种类和活性均低于清洁土壤。微生物群落主成分分析(PCA)表明,石油污染土壤和清洁土壤的微生物群落存在显著差异(P0.01),起分异作用的碳源主要为糖类,其次是羧酸类和氨基酸类;随着土壤石油含量增加,典型变量值变异(离散)增大,土壤微生物群落结构稳定性降低。微生物群落多样性分析表明,Shannon丰富度指数(H)、McIntosh均一度指数(U)和Simpson优势度指数(1/D)均达到极显著差异(P0.01),污染土壤微生物群落H和U低于清洁土壤,但是一定浓度的石油污染可以刺激土壤微生物群落中优势种群的生长,1/D增高。研究结果为陕北黄土高原石油污染区土壤微生物修复提供理论基础。

Microbial community structure and metabolic characteristics of oil-contaminated soil in the Loess Plateau

To investigate the impacts of crude oil pollution on the soil microbial community, and estimate the potential for crude oil degradation by indigenous microbial consortia, we examined the soil microbial community structure, metabolic characteristics and functional diversity of crude oil-contaminated soil collected in the Loess Plateau in northern Shaanxi, using plate counts and the Biolog Eco plate method. The results showed that the responses of soil microbes to crude oil pollution stress varied greatly. The abundance of bacteria and fungi in crude oil-contaminated soil were about one order of magnitude higher than in the uncontaminated soil, while the abundance of actinomycetes was significantly lower in polluted soil than in uncontaminated soil (P < 0.01). The number of bacteria in crude oil-contaminated soil was 10⁷ CFU/g, and the proportion of bacteria reached 99.8%-99.9% of all microbes. This indicated that majority of the crude oil biodegradation was the result of bacterial activity in collaboration with fungi rather than actinomycetes. The microbial activity of uncontaminated soil was higher than that of crude oil-contaminated soil, and microbial activity decreased with increased concentrations of crude oil. This phenomenon can be easily explained by the fact that the microbial metabolic activity had been affected owing to an increase in carbon sources and an imbalance in the soil nutrient ratio followed by an increase in the crude oil concentration in soil. The microbes in both crude oil-contaminated and uncontaminated soil were more likely to use carbon sources such as carbohydrates and polymers on the Biolog plates. Microbes from crude oil-contaminated soil used less of the available carbon sources and showed lower metabolic activity than microbes from the uncontaminated soil. This indicated that soil microbes adapted to the crude oil-contaminated environment by adjusting the microbial community structure, and a correlation was observed between the soil microbial community structure and soil microbial growth. The principal component analyses results revealed a significant difference (P < 0.01) in soil microbial community structure between uncontaminated and crude oil-contaminated soils. The differences mostly related to the use of carbohydrates as the dominant carbon source and then carboxylic acids and amino acids. The variation in the canonical variable (discrete value) increased with increasing soil crude oil content, however, the stability of the soil microbial community structure decreased. This indicated that the crude oil pollutant destroyed the original soil ecological environment. The diversity of microbial community, as indicated by Shannon (H), McIntosh (U), and Simpson (1/D) indices, was significantly different in crude oil-contaminated soil (P < 0.01) compared with uncontaminated soil. H and U values were lower in crude oil-contaminated soil than in uncontaminated soil, and 1/D was higher in crude oil-contaminated soil than in uncontaminated soil. This phenomenon was likely due to the stimulating effect of certain levels of crude oil on the growth of the dominant microbial community. The findings stated above provide a basis for bioremediation of oil-contaminated soil in the Loess Plateau in northern Shaanxi. These results are especially important because they indicated that the soil in the Loess Plateau in northern Shaanxi shows good potential for bioremediation, and crude oil contamination in the soil could be degraded by indigenous microbes with the addition of nitrogen and phosphorus. An additional benefit is that it leads to an improved evaluation of the bioremediation potential of the indigenous microbial consortia.