Li Yaying,Zhang Yang,Chapman Stephen James,Yao Huaiying
Sorghum has a great capacity to release biological nitrification inhibitors (BNIs), but the inhibitory effect on nitrification and ammonia oxidizer populations under planted soil conditions is unclear. A pot experiment with three nitrogen (N) application rates (0, 50, and 200 mg N kg −1 ) was set up to detect the influence of sorghum growth on soil nitrification and investigate the function of blocking the activity of ammonia oxidizers. A 15 N-labeled experiment was also conducted to detect the N form absorbed by sorghum. Sorghum root exudates were collected at 30 days after transplanting to hydroponic culture and added into cultured soil to determine the shifts in the populations of nitrifiers. The 15 N labeling experiment showed that the uptake rate by sorghum of ammonium N fertilizer was 24% and that of nitrate N fertilizer was 9%, indicating that sorghum was an ammonium using plant. Compared with unplanted soil, sorghum planting had a significant inhibitory effect on the nitrification process even at the high-N fertilizer rates. Autotrophic nitrification was the prevailing process, and sorghum root exudation inhibited this process as much as dicyandiamide (DCD, 10 mg kg −1 ). Root exudates had a significant inhibitory effect on ammonia-oxidizing bacteria (AOB) but had no effect on ammonia-oxidizing archaea (AOA).
The estuarine plastisphere, a novel ecological habitat in the Anthropocene, has garnered global concerns. Recent geochemical evidence has pointed out its potential role in influencing nitrogen biogeochemistry. However, the biogeochemical significance of the plastisphere and its mechanisms regulating nitrogen cycling remain elusive. Using 15 N- and 13 C-labelling coupled with metagenomics and metatranscriptomics, here we unveil that the plastisphere likely acts as an underappreciated nitrifying niche in estuarine ecosystems, exhibiting a 0.9 ~ 12-fold higher activity of bacteria-mediated nitrification compared to surrounding seawater and other biofilms (stone, wood and glass biofilms). The shift of active nitrifiers from O 2 -sensitive nitrifiers in the seawater to nitrifiers with versatile metabolisms in the plastisphere, combined with the potential interspecific cooperation of nitrifying substrate exchange observed among the plastisphere nitrifiers, collectively results in the unique nitrifying niche. Our findings highlight the plastisphere as an emerging nitrifying niche in estuarine environment, and deepen the mechanistic understanding of its contribution to marine biogeochemistry.
Liu Haiyang,Pan Hong,Hu Hangwei,Jia Zhongjun,Zhang Qian,Liu Yimeng,Xu Jianming,Di Hongjie,Li Yong
Aims Previous studies suggest that organic carbon (C) and nitrogen (N) can stimulate soil nitrification, but whether autotrophic or heterotrophic nitrification is stimulated and who are active nitrifiers for the nitrification activity is still in debate. We elucidated which nitrification dominated and the active nitrifiers during the decomposition of rice callus. Methods 15 N-labeled callus and acetylene (C 2 H 2 ) inhibition were used to explore the autotrophic or heterotrophic nitrification during the decomposition of callus and DNA-based stable isotope probing (SIP) and high-throughput sequencing were used to investigate the active nitrifiers. Results Autotrophic nitrification dominated the nitrification activity, driven by oxidation of ammonia (NH 3 ) produced from mineralization of the callus-derived organic N. Callus significantly stimulated nitrification activity, which was paralleled by changes in the abundance and community composition of AOA. DNA-SIP further demonstrated that the active AOA outnumbered their bacterial counterparts in the 13 C-DNA from the soil with callus amendment. Phylogenetic analysis revealed the functional importance of soil fosmid 29i4-like and 54d9-like AOA within soil group 1.1b during the active nitrification with callus cells. Conclusions NH 3 released from the mineralization of callus was the main substrate for autotrophic nitrification and preferentially stimulated the growth of AOA within group 1.1b in the paddy soil.
危险品化学品经营许可证（带存储）