Plugge Caroline M, Zhang Weiwen, Scholten Johannes C M, Stams Alfons J M
Laboratory of Microbiology, Wageningen University Wageningen, Netherlands.
Front Microbiol. 2011 May 2;2:81. doi: 10.3389/fmicb.2011.00081. eCollection 2011.
Dissimilatory sulfate-reducing prokaryotes (SRB) are a very diverse group of anaerobic bacteria that are omnipresent in nature and play an imperative role in the global cycling of carbon and sulfur. In anoxic marine sediments sulfate reduction accounts for up to 50% of the entire organic mineralization in coastal and shelf ecosystems where sulfate diffuses several meters deep into the sediment. As a consequence, SRB would be expected in the sulfate-containing upper sediment layers, whereas methanogenic archaea would be expected to succeed in the deeper sulfate-depleted layers of the sediment. Where sediments are high in organic matter, sulfate is depleted at shallow sediment depths, and biogenic methane production will occur. In the absence of sulfate, many SRB ferment organic acids and alcohols, producing hydrogen, acetate, and carbon dioxide, and may even rely on hydrogen- and acetate-scavenging methanogens to convert organic compounds to methane. SRB can establish two different life styles, and these can be termed as sulfidogenic and acetogenic, hydrogenogenic metabolism. The advantage of having different metabolic capabilities is that it raises the chance of survival in environments when electron acceptors become depleted. In marine sediments, SRB and methanogens do not compete but rather complement each other in the degradation of organic matter. Also in freshwater ecosystems with sulfate concentrations of only 10-200 μM, sulfate is consumed efficiently within the top several cm of the sediments. Here, many of the δ-Proteobacteria present have the genetic machinery to perform dissimilatory sulfate reduction, yet they have an acetogenic, hydrogenogenic way of life. In this review we evaluate the physiology and metabolic mode of SRB in relation with their environment.
异化硫酸盐还原原核生物（SRB）是一类非常多样的厌氧细菌，在自然界中无处不在，在全球碳和硫的循环中起着至关重要的作用。在缺氧的海洋沉积物中，硫酸盐还原占沿海和陆架生态系统中整个有机矿化的50%，在这些生态系统中，硫酸盐会扩散到沉积物中数米深的地方。因此，预计在含硫酸盐的上层沉积层中会有SRB，而产甲烷古菌预计会在沉积物中更深的硫酸盐耗尽层中占主导。在沉积物中有机物含量高的地方，硫酸盐在浅沉积深度就会被耗尽，从而会发生生物成因甲烷的产生。在没有硫酸盐的情况下，许多SRB会发酵有机酸和醇，产生氢气、乙酸和二氧化碳，甚至可能依靠清除氢气和乙酸的产甲烷菌将有机化合物转化为甲烷。SRB可以建立两种不同的生活方式，可将其称为硫化物生成型和乙酸生成型、产氢代谢。具有不同代谢能力的优势在于，当电子受体耗尽时，它增加了在环境中生存的机会。在海洋沉积物中，SRB和产甲烷菌在有机物降解过程中并非相互竞争，而是相互补充。同样，在硫酸盐浓度仅为10 - 200μM的淡水生态系统中，硫酸盐在沉积物顶部几厘米内就被有效消耗。在这里，许多存在的δ-变形菌具有进行异化硫酸盐还原的遗传机制，但它们具有乙酸生成型、产氢的生活方式。在本综述中，我们评估了SRB与其环境相关的生理学和代谢模式。
