Department of Microbiology, Cornell University, Ithaca, New York 14853.
Appl Environ Microbiol. 1987 May;53(5):1157-63. doi: 10.1128/aem.53.5.1157-1163.1987.
Sediment core samples were obtained at a groundwater study site in Oklahoma in January and June 1985. Most-probable-number estimates showed that protozoan numbers declined steeply with depth in subsoil. Flagellates and amoebae dominated the protozoan population, which declined to a most probable number of 28 . g (dry weight) in a clay loam layer at the bottom of the unsaturated zone. Samples from a texturally variable interface zone between 3 and 4 m down also were variable in their content of protozoa. Four contiguous clay loam samples in a single core from this zone contained variable numbers of amoebae ranging from 0.2 to 44 . g (dry weight). However, a sandy clay loam layer at the bottom of the core contained a mixture of flagellates and amoebae with a combined population density of 67 . g (dry weight). A slow-growing filose amoeba was isolated from interface zone samples and was tentatively classified in a new family in the order Aconchulinida. Protozoa were not detected in the saturated zone except in a very permeable gravelly, loamy sand layer at a depth of approximately 7.5 m. Low numbers (4 to 6 . g [dry weight]) of surface-type flagellates and amoebae, as well as the filose amoeba seen in the interface zone, were observed in this layer. Acid-treated and untreated samples contained equivalent numbers of protozoa, showing that the majority of protozoa in the layer at 7.5 m and the interface zone samples were encysted. Increased numbers of bacteria also were found in the layer at 7.5 m, indicating that it was biologically more active than other saturated-zone layers. Cyanobacteria grew in illuminated samples from this layer, suggesting that it may be connected hydrologically to a nearby river.
1985 年 1 月和 6 月，在俄克拉荷马州的一个地下水研究点获取了沉积物岩芯样本。最可能数量估计表明，原生动物数量在土壤下部随深度急剧下降。鞭毛虫和变形虫在原生动物种群中占主导地位，在不饱和带底部的粘壤土层中，最可能数量下降到 28. g（干重）。来自 3 至 4 米深处质地变化的界面区的样本在原生动物含量方面也存在差异。该区域单个岩芯的四个连续粘壤土样本中，变形虫数量从 0.2 到 44. g（干重）不等。然而，岩芯底部的砂质粘壤土层含有混合的鞭毛虫和变形虫，其种群密度为 67. g（干重）。从界面区样本中分离出一种生长缓慢的丝状变形虫，并暂定分类在一个新的 Aconchulinida 目中的一个新科中。除了在深度约为 7.5 米的非常透水的砾石、壤土砂层中，在饱和带中未检测到原生动物。在该层中观察到数量较少（4 至 6. g[干重]）的表面型鞭毛虫和变形虫以及在界面区中观察到的丝状变形虫。经酸处理和未经处理的样本中含有等量的原生动物，表明在 7.5 米处的层和界面区样本中的大多数原生动物处于囊胞状态。在 7.5 米处的层中还发现了更多的细菌，表明其比其他饱和带层具有更高的生物活性。蓝细菌在来自该层的光照样本中生长，表明它可能在水文学上与附近的河流相连。
