title: Nitrous oxide reductase gene (nosZ) and N2O reduction along the littoral gradient of a eutrophic freshwater lake.
abstract: Lake littoral zones are characterized by heterogeneity in the biogeochemistry of nutrient elements. This study aimed to explore the relationship between the nitrous oxide reductase gene (nosZ)-encoding denitrifier community composition/abundance and N2O reduction. Five samples (deep sediment, near-transition sediment, transition site, near-transition land and land soil) were collected along a littoral gradient of eutrophic Baiyangdian Lake, North China. To investigate the relationship between the nosZ-encoding denitrifier community structure and N2O reduction, the nosZ-encoding denitrifier community composition/abundance, potential denitrification rate (DNR) and potential N2O production rate (pN2O) were investigated using molecular biological technologies and laboratory incubation experiments. The results showed that the average DNR of sediments was about 25 times higher than that of land soils, reaching 282.5 nmol N/(g dry weight (dw) x hr) and that the average pN2O of sediments was about 3.5 times higher than that of land soils, reaching 15.7 nmol N/(g dw x hr). In the land area, the nosZ gene abundance showed a negative correlation with the N2O/(N2O + N2) ratio, indicating that nosZ gene abundance dominated N2O reduction both in the surface soils of the land area and in the soil core of the transition site. Phylogenetic analysis showed that all the nosZ sequences recovered from sediment clustered closely with the isolates Azospirillum largimobile and Azospirillum irakense affiliated to Rhodospirillaceae in alpha-Proteobacteria, while about 92.3% (12/13) of the nosZ sequences recovered from land soil affiliated to Rhizobiaceae and Bradyrhizobiaceae in alpha-Proteobacteria. The community composition of nosZ gene-encoding denitrifiers appeared to be coupled with N2O reduction along the littoral gradient.
authors.affiliation: State Key Laboratory of Environmental Aquatic Quality, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. cxwang127@126.com
authors.forename: Chaoxu
authors.initials: C
authors.lastname: Wang
authors.forename: Guibing
authors.initials: G
authors.lastname: Zhu
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Shanyun
authors.initials: S
authors.lastname: Wang
authors.forename: Chengqing
authors.initials: C
authors.lastname: Yin
mesh_terms: D020561:Alphaproteobacteria / Q000302:isolation & purification / Q000378:metabolism; D016949:Azospirillum / Q000378:metabolism; D002681:China; D005618:Fresh Water; D019015:Geologic Sediments / Q000032:analysis; D060106:Lakes; D009609:Nitrous Oxide / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D012230:Rhizobiaceae / Q000302:isolation & purification / Q000378:metabolism; D012988:Soil Microbiology
chemical_list: D010088:Oxidoreductases; C022763:nitrous oxide reductase; D009609:Nitrous Oxide