Herrmann M, Opitz S, Harzer R, Totsche K U, Küsel K
Aquatic Geomicrobiology, Institute of Ecology, Friedrich Schiller University Jena, Dornburger Strasse 159, 07743, Jena, Germany.
German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.
Microb Ecol. 2017 Aug;74(2):264-277. doi: 10.1007/s00248-017-0950-x. Epub 2017 Feb 18.
Oxygen and nitrate availability as well as the presence of suitable organic or inorganic electron donors are strong drivers of denitrification; however, the factors influencing denitrifier abundance and community composition in pristine aquifers are not well understood. We explored the denitrifier community structure of suspended and attached groundwater microorganisms in two superimposed limestone aquifer assemblages with contrasting oxygen regime in the Hainich Critical Zone Exploratory (Germany). Attached communities were retrieved from freshly crushed parent rock material which had been exposed for colonization in two groundwater wells (12.7 and 48 m depth). Quantitative PCR and amplicon pyrosequencing of nirK and nirS genes encoding copper-containing or cytochrome cd1 heme-type nitrite reductase, respectively, and of bacterial 16S ribosomal RNA genes showed a numerical predominance of nirS-type denitrifiers in both attached and suspended groundwater communities and a dominance of nirS-type denitrifiers closely related to the autotrophic thiosulfate- and hydrogen-oxidizing Sulfuritalea hydrogenivorans and the iron- and sulfide-oxidizing Sideroxydans lithotrophicus ES-1. Potential rates of nitrate reduction in association with exposed crushed rock material were higher with an inorganic electron donor (thiosulfate) compared to an organic electron donor (fumarate/acetate) in the upper aquifer assemblage but similar in the lower, oxic aquifer. Our results have clearly demonstrated that groundwater from pristine limestone aquifers harbors diverse denitrifier communities which appear to selectively attach to rock surfaces and harbor a high potential for nitrate reduction. Our findings suggest that the availability of suitable inorganic versus organic electron donors rather than oxygen availability shapes denitrifier communities and their potential activity in these limestone aquifers.
氧气和硝酸盐的可利用性以及合适的有机或无机电子供体的存在是反硝化作用的强大驱动因素；然而，影响原始含水层中反硝化菌丰度和群落组成的因素尚未得到充分了解。我们在德国海尼希关键带探索区的两个具有不同氧气状况的叠加石灰岩含水层组合中，研究了悬浮和附着的地下水微生物的反硝化菌群落结构。附着群落取自新鲜破碎的母岩材料，这些母岩材料已在两口地下水井（深度分别为12.7米和48米）中暴露以供定殖。对分别编码含铜或细胞色素cd1血红素型亚硝酸还原酶的nirK和nirS基因以及细菌16S核糖体RNA基因进行定量PCR和扩增子焦磷酸测序，结果表明，在附着和悬浮的地下水群落中，nirS型反硝化菌在数量上占优势，且nirS型反硝化菌主要与自养的硫代硫酸盐和氢气氧化的嗜氢硫杆菌以及铁和硫化物氧化的嗜铁氧化亚铁杆菌ES-1密切相关。在上层含水层组合中，与无机电子供体（硫代硫酸盐）相比，与暴露的破碎岩石材料相关的硝酸盐还原潜在速率在有机电子供体（富马酸盐/乙酸盐）存在时更高，但在下层有氧含水层中相似。我们的结果清楚地表明，原始石灰岩含水层中的地下水含有多样的反硝化菌群落，这些群落似乎会选择性地附着在岩石表面，并且具有很高的硝酸盐还原潜力。我们的研究结果表明，合适的无机与有机电子供体的可利用性而非氧气的可利用性决定了这些石灰岩含水层中反硝化菌群落及其潜在活性。
