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首页> 外文期刊>Applied and Environmental Microbiology >Vertical Migration in the Sediment-Dwelling Sulfur Bacteria Thioploca spp. in Overcoming Diffusion Limitations.
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Vertical Migration in the Sediment-Dwelling Sulfur Bacteria Thioploca spp. in Overcoming Diffusion Limitations.

机译：沉积物中的硫细菌Thioploca spp中的垂直迁移。克服扩散限制。

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In order to investigate the environmental requirements of the filamentous sulfur bacteria Thioploca spp., we tested the chemotactic responses of these sedimentary microorganisms to changes in oxygen, nitrate, and sulfide concentrations. A sediment core with a Thioploca mat, retrieved from the oxygen-minimum zone on the Chilean shelf, was incubated in a recirculating flume. The addition of 25 (mu)mol of nitrate per liter to the seawater flow induced the ascent of the Thioploca trichomes (length, up to 70 mm) in their mostly vertically oriented gelatinous sheaths. The upper ends of the filaments penetrated the sediment surface and protruded 1 to 3 mm into the flowing water before they bent downstream. By penetrating the diffusive boundary layer, Thioploca spp. facilitate efficient nitrate uptake in exposed trichome sections that are up to 30 mm long. The cumulative length of exposed filaments per square centimeter of sediment surface was up to 92 cm, with a total exposed trichome surface area of 1 cm(sup2). The positive reaction to nitrate overruled a negative response to oxygen, indicating that nitrate is the principal electron acceptor used by Thioploca spp. in the anoxic environment; 10-fold increases in nitrate fluxes after massive emergence of filaments strengthened this hypothesis. A positive chemotactic response to sulfide concentrations of less than 100 (mu)mol liter(sup-1) counteracted the attraction to nitrate and, along with phobic reactions to oxygen and higher sulfide concentrations, controlled the vertical movement of the trichomes. We suggest that the success of Thioploca spp. on the Chilean shelf is based on the ability of these organisms to shuttle between the nitrate-rich boundary layer and the sulfidic sediment strata.
机译：为了调查丝状硫细菌Thioploca spp。的环境要求，我们测试了这些沉积微生物对氧，硝酸盐和硫化物浓度变化的趋化反应。从智利架上的氧气最小区域取回的带有Thioploca垫的沉积芯在循环水槽中孵育。向海水中每升添加25μmol硝酸盐会导致Thioploca毛状体（长度最多70毫米）在其大部分垂直取向的胶状鞘中上升。细丝的上端穿透沉积物表面，并在向下游弯曲之前向流动的水中突出1-3毫米。通过穿透扩散边界层，Thioploca spp。有助于在长达30 mm的裸露毛线部分中有效吸收硝酸盐。每平方厘米沉积物表面暴露的长丝累积长度最大为92 cm，总暴露的毛状体表面积为1 cm（sup2）。对硝酸盐的正反应超过对氧气的负反应，这表明硝酸盐是Thioploca spp使用的主要电子受体。在缺氧的环境中;在细丝大量出现后，硝酸盐通量增加了10倍，从而加强了这一假设。硫化物浓度低于100（μmol）升（sup-1）的正趋化反应抵消了对硝酸盐的吸引，并与对氧气的恐惧反应和更高的硫化物浓度控制了毛线虫的垂直运动。我们建议Thioploca spp成功。智利大陆架上的生物是基于这些生物在富含硝酸盐的边界层和硫化物沉积物层之间穿梭的能力。

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