Ultrastructure and geochemistry of endolithic microorganisms in limestone of the Niagara Escarpment
Ultrastructure and geochemistry of endolithic microorganisms in limestone of the Niagara Escarpment
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DOI：
10.1139/m97-029
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发表时间：
1997-03-01
影响因子：
2.8
通讯作者：
Lowson, EA
中科院分区：
文献类型：
--
作者：
Ferris, FG;Lowson, EA
以光合蓝藻为主的内生微生物群落出现在形成加拿大安大略省尼亚加拉悬崖垂直悬崖的白云岩灰岩内部0.5-3.0 mm的深度。通过差示干涉对比和主荧光显微镜检查，在定植岩石样品中，球虫Gloeocapsa是最突出的蓝藻种。丝状蓝藻的种类是不常见的比球藻形式，但可以很容易地区分在所有载玻片制剂。扫描电子显微镜显示，内石发生在位于石灰岩开放孔隙空间内的公共种群中。异养细菌也被观察到作为附生体生长在死蓝藻和活蓝藻上，并在孔空间壁上的附生生物膜中生长。在透射电子显微镜检查的薄切片标本中，这些粘附细菌通常在其细胞壁外表现出纤维胞外聚合物材料的广泛积累。根据样品中有机磷含量估算的生物量浓度与岩石孔隙度基本一致，范围为干重的3.3 ~ 17.1%。碳同位素（C-14）测量表明，大气中的二氧化碳被内生蓝藻所利用，而不是石灰岩寄主岩石中碳酸盐矿物风化过程中溶解的无机碳。此外，整个岩石的多元素分析显示，在宿主岩石上方的内岩带中，某些元素（如磷、钡、铅和锌）富集，而其他元素（如镁、钙、铁和铜）则缺乏。这表明，内生微生物在尼亚加拉断崖面生态系统营养元素和微量元素的生物地球化学循环中起着积极的作用。
Endolithic microbial communities dominated by photosynthetic cyanobacteria occur at a depth of 0.5-3.0 mm inside dolomitic limestone that forms the vertical cliffs of the Niagara Escarpment in Ontario, Canada. Coccoid Gloeocapsa was the most prominent cyanobacterial species in colonized rock samples examined by differential interference contrast and episcopic fluorescent microscopy. Filamentous varieties of cyanobacteria were less common than coccoid forms but could be easily distinguished in all slide mount preparations. Scanning electron microscopy showed that the endoliths occurred in communal populations situated within the open pore spaces of the limestone. Heterotrophic bacteria were also observed growing as epiphytes on dead and living cyanobacteria, and in epilithic biofilms on pore space walls. In thin-sectioned specimens examined by transmission electron microscopy, these adherent bacteria commonly exhibited extensive accumulations of fibrous extracellular polymeric materials external to their cell walls. Biomass concentrations, estimated from the organic phosphorus content of the samples, generally paralleled rock porosity and ranged from 3.3 to 17.1% dry weight. Carbon isotope (C-14) measurements indicated that atmospheric carbon dioxide is used by the endolithic cyanobacteria, rather than dissolved inorganic carbon from the weathering of carbonate minerals in the limestone host rock. In addition, whole rock multielement analyses revealed an enrichment of some elements (e.g., phosphorus, barium, lead, and zinc) in the endolith zone over the host rock, while other elements (e.g., magnesium, calcium, iron, and copper) were depleted. The implication is that the endolithic microorganisms play an active role in the biogeochemical cycling of nutrient and trace elements in cliff face ecosystems of the Niagara Escarpment.