Anaerobic oxidation of ammonium (anammox) is recognized as an important process for nitrogen (N) cycling, yet its role in agricultural ecosystems, which are intensively fertilized, remains unclear. In this study, we investigated the presence, activity, functional gene abundance and role of anammox bacteria in rhizosphere and non-rhizosphere paddy soils using catalyzed reporter deposition–fluorescence in situ hybridization, isotope-tracing technique, quantitative PCR assay and 16S rRNA gene clone libraries. Results showed that rhizosphere anammox contributed to 31–41% N2 production with activities of 0.33–0.64 nmol N2 g−1 soil h−1, whereas the non-rhizosphere anammox bacteria contributed to only 2–3% N2 production with lower activities of 0.08–0.26 nmol N2 g−1 soil h−1. Higher anammox bacterial cells were observed (0.75–1.4 × 107 copies g−1 soil) in the rhizosphere, which were twofold higher compared with the non-rhizosphere soil (3.7–5.9 × 106 copies g−1 soil). Phylogenetic analysis of the anammox bacterial 16S rRNA genes indicated that two genera of ‘Candidatus Kuenenia' and ‘Candidatus Brocadia' and the family of Planctomycetaceae were identified. We suggest the rhizosphere provides a favorable niche for anammox bacteria, which are important to N cycling, but were previously largely overlooked.
展开▼
机译:氨(厌氧氨)的厌氧氧化被认为是氮(N)循环的重要过程,但在集约化施肥的农业生态系统中的作用仍不清楚。在这项研究中,我们使用催化的报告分子沉积-荧光原位杂交,同位素示踪技术,定量PCR分析和16S rRNA基因克隆研究了根际和非根际稻田土壤中厌氧氨氧化细菌的存在,活性,功能基因丰度以及其作用。库。结果表明,根际厌氧菌对N2的贡献为31–41%,其活性为0.33–0.64 nmol N2 g −1 sup> soil h −1 sup>,而非根际厌氧菌仅贡献了2–3%的N2产量,而较低的活性为0.08–0.26 nmol N2 g -1 sup>土壤h -1 sup>。在根际中观察到较高的厌氧菌细菌细胞(0.75–1.4×10 7 sup> copies g −1 sup>土壤),比非根际土壤高3.7倍。 –5.9×10 6 sup>复制g −1 sup>土壤)。对厌氧细菌厌氧菌16S rRNA基因的系统进化分析表明,已鉴定出“ Candidatus Kuenenia”和“ Candidatus Brocadia”两个属以及扁平菌科。我们建议,根际为厌氧细菌提供了有利的利基,这对氮循环很重要,但以前被很大程度上忽略了。
展开▼