Lücker Sebastian, Schwarz Jasmin, Gruber-Dorninger Christiane, Spieck Eva, Wagner Michael, Daims Holger
Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria.
University of Hamburg, Biocenter Klein Flottbek, Microbiology and Biotechnology, Hamburg, Germany.
ISME J. 2015 Mar;9(3):708-20. doi: 10.1038/ismej.2014.158. Epub 2014 Sep 2.
Numerous past studies have shown members of the genus Nitrospira to be the predominant nitrite-oxidizing bacteria (NOB) in nitrifying wastewater treatment plants (WWTPs). Only recently, the novel NOB 'Candidatus Nitrotoga arctica' was identified in permafrost soil and a close relative was enriched from activated sludge. Still, little is known about diversity, distribution and functional importance of Nitrotoga in natural and engineered ecosystems. Here we developed Nitrotoga 16S rRNA-specific PCR primers and fluorescence in situ hybridization (FISH) probes, which were applied to screen activated sludge samples from 20 full-scale WWTPs. Nitrotoga-like bacteria were detected by PCR in 11 samples and reached abundances detectable by FISH in seven sludges. They coexisted with Nitrospira in most of these WWTPs, but constituted the only detectable NOB in two systems. Quantitative FISH revealed that Nitrotoga accounted for nearly 2% of the total bacterial community in one of these plants, a number comparable to Nitrospira abundances in other WWTPs. Spatial statistics revealed that Nitrotoga coaggregated with ammonia-oxidizing bacteria, strongly supporting a functional role in nitrite oxidation. This activity was confirmed by FISH in combination with microradiography, which revealed nitrite-dependent autotrophic carbon fixation by Nitrotoga in situ. Correlation of the presence or absence with WWTP operational parameters indicated low temperatures as a main factor supporting high Nitrotoga abundances, although in incubation experiments these NOB remained active over an unexpected range of temperatures, and also at different ambient nitrite concentrations. In conclusion, this study demonstrates that Nitrotoga can be functionally important nitrite oxidizers in WWTPs and can even represent the only known NOB in engineered systems.
过去大量研究表明，硝化螺旋菌属成员是硝化污水处理厂（WWTPs）中主要的亚硝酸盐氧化细菌（NOB）。直到最近，新型NOB“北极嗜硝化菌（暂未培养）”才在永久冻土中被鉴定出来，并且从活性污泥中富集到了其近亲。然而，对于嗜硝化菌属在自然和工程生态系统中的多样性、分布及功能重要性仍知之甚少。在此，我们开发了嗜硝化菌属16S rRNA特异性PCR引物和荧光原位杂交（FISH）探针，并将其应用于对20个全规模污水处理厂活性污泥样本的筛选。通过PCR在11个样本中检测到了嗜硝化菌属样细菌，在7个污泥样本中其丰度达到了可通过FISH检测到的水平。在大多数这些污水处理厂中，它们与硝化螺旋菌共存，但在两个系统中是唯一可检测到的NOB。定量FISH显示，在其中一个工厂中，嗜硝化菌属占细菌群落总数的近2%，这一数量与其他污水处理厂中硝化螺旋菌的丰度相当。空间统计显示，嗜硝化菌与氨氧化细菌共聚集，有力地支持了其在亚硝酸盐氧化中的功能作用。通过FISH结合微射线照相术证实了这种活性，该技术揭示了嗜硝化菌在原位进行依赖亚硝酸盐的自养碳固定。存在与否与污水处理厂运行参数的相关性表明，低温是支持嗜硝化菌高丰度的主要因素，尽管在培养实验中，这些NOB在出乎意料的温度范围内以及不同的环境亚硝酸盐浓度下仍保持活性。总之，本研究表明，嗜硝化菌在污水处理厂中可能是功能重要的亚硝酸盐氧化菌，甚至在工程系统中可能是唯一已知的NOB。
