Ramsing N B, Ferris M J, Ward D M
Department of Microbial Ecology, Institute of Biological Sciences, University of Aarhus, DK-8000 Aarhus C, Denmark.
Appl Environ Microbiol. 2000 Mar;66(3):1038-49. doi: 10.1128/AEM.66.3.1038-1049.2000.
A variety of contemporary techniques were used to investigate the vertical distribution of thermophilic unicellular cyanobacteria, Synechococcus spp., and their activity within the upper 1-mm-thick photic zone of the mat community found in an alkaline siliceous hot spring in Yellowstone National Park in Wyoming. Detailed measurements were made over a diel cycle at a 61 degrees C site. Net oxygenic photosynthesis measured with oxygen microelectrodes was highest within the uppermost 100- to 200-microm-thick layer until midmorning, but as the day progressed, the peak of net activity shifted to deeper layers, stabilizing at a depth of 300 microm from midday throughout the afternoon. Examination of vertical thin sections by bright-field and autofluorescence microscopy revealed the existence of different populations of Synechococcus which form discrete bands at different vertical positions. Denaturing gradient gel electrophoresis analysis of PCR-amplified 16S rRNA gene segments from horizontal cryosections obtained at 100-microm-thick vertical intervals also suggested vertical stratification of cyanobacterial, green sulfur bacterium-like, and green nonsulfur bacterium-like populations. There was no evidence of diel migration. However, image analysis of vertical thin sections revealed the presence of a narrow band of rod-shaped Synechococcus cells in which the cells assumed an upright position. These upright cells, located 400 to 800 microm below the surface, were observed only in mat samples obtained around noon. In mat samples obtained at other time points, the cells were randomly oriented throughout the mat. These combined observations reveal the existence of a highly ordered structure within the very thin photic zone of this hot spring microbial mat, consisting of morphologically similar Synechococcus populations that are likely to be differentially adapted, some co-occurring with green sulfur bacterium-like populations, and all overlying green nonsulfur bacterium-like populations.
运用了多种当代技术来研究嗜热单细胞蓝藻（聚球藻属）的垂直分布及其在怀俄明州黄石国家公园碱性硅质温泉中发现的席状群落上部1毫米厚光合层内的活性。在一个61摄氏度的地点进行了一个昼夜周期的详细测量。用氧微电极测量的净产氧光合作用在最上层100至200微米厚的层内直到上午中旬都是最高的，但随着一天的进展，净活性峰值转移到更深的层，从中午到整个下午稳定在300微米的深度。通过明场和自发荧光显微镜检查垂直薄片，发现聚球藻存在不同种群，它们在不同垂直位置形成离散带。对从以100微米厚垂直间隔获得的水平冷冻切片中PCR扩增的16S rRNA基因片段进行变性梯度凝胶电泳分析，也表明蓝藻、绿硫细菌样和绿色非硫细菌样种群存在垂直分层。没有昼夜迁移的证据。然而，垂直薄片的图像分析显示存在一条窄带的杆状聚球藻细胞，其中细胞呈直立位置。这些直立细胞位于表面以下400至800微米处，仅在中午左右获得的席状样本中观察到。在其他时间点获得的席状样本中，细胞在整个席状物中随机取向。这些综合观察结果揭示了该温泉微生物席极薄光合层内存在高度有序的结构，由形态相似的聚球藻种群组成，这些种群可能具有不同的适应性，一些与绿硫细菌样种群共存，并且都覆盖着绿色非硫细菌样种群。
