Geochemistry, fatty acid content and phylogenetic affiliation of soil samples from Livingston Island, South Shetland Archipelago, Antarctica

Microorganisms inhabit very different soil habitats in the ice-free areas of Antarctica, playing a major role in nutrient cycling in cold environments. We studied the soil characteristics and the dominant bacterial composition from nine different soil profiles located on Livingston Island (maritime Antarctica). The total carbon (TC) and total nitrogen (TN) values were high for the vegetated soils, decreasing with depth, whereas the values for the mineral soils were generally low. Soil pH was more acidic for moss-covered soils and neutral to alkaline for mineral soils. Numbers of culturable heterotrophic bacteria were higher at vegetated sites, but significant numbers were also detectable in carbon-depleted soils. Patterns of denaturing gradient gel electrophoresis (DGGE) revealed a highly heterogeneous picture throughout the soil profiles. Subsequent sequencing of DGGE bands revealed in total 252 sequences that could be assigned to 114 operational taxonomic units, showing the dominance of members of the Bacteroidetes and Acidobacteria. The results of phospholipid fatty acid analysis showed a lack of unsaturated fatty acids for most of the samples. Samples with a prevalence of unsaturated over saturated fatty acids were restricted to several surface samples. Statistical analysis showed that the dominant soil bacterial community composition is most affected by TC and TN contents and soil physical factors such as grain size and moisture, but not pH.
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微生物栖息于南极无冰区差异显著的各类土壤生境中，在寒冷环境的养分循环中发挥核心作用。本研究针对南极海洋性区域利文斯顿岛的9处不同土壤剖面，开展了土壤特性与优势细菌群落组成的研究。植被覆盖土壤的总碳（TC）与总氮（TN）含量较高，且随土层深度增加呈下降趋势；而矿质土壤的总碳、总氮含量普遍较低。苔藓覆盖土壤的pH值偏酸性，矿质土壤的pH值则多呈中性至碱性。可培养异养细菌的数量在植被覆盖样点更高，但在贫碳土壤中也可检测到可观的菌群数量。变性梯度凝胶电泳（denaturing gradient gel electrophoresis, DGGE）图谱显示，所有土壤剖面的细菌群落均呈现高度异质性。后续对DGGE条带的测序结果表明，共获得252条有效序列，可归为114个操作分类单元（operational taxonomic units, OTU），其中拟杆菌门（Bacteroidetes）与酸杆菌门（Acidobacteria）的类群占主导地位。磷脂脂肪酸分析结果显示，多数样品中未检测到不饱和脂肪酸；不饱和脂肪酸占比高于饱和脂肪酸的样品仅局限于少数表层土壤样品。统计分析表明，土壤优势细菌群落组成主要受总碳、总氮含量，以及粒径、含水率等土壤物理因子的影响，而与pH值无显著关联。关键词