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The stable isotope technique has been used in tracking nitrogen cycling processes, but the isotopic characteristics are influenced by environmental conditions. To better understand the variability of nitrate isotopes in nature, we investigated the influence of organic carbon sources on isotope fractionation characteristics during microbial denitrification. Denitrifying cultures were inoculated with freshwater samples and enriched with five forms of organic compounds, that is, acetate, citrate, glucose, cellobiose, and leucine. Though the isotope enrichment factors of nitrogen and oxygen (15ε and 18ε) changed with carbon sources, 18ε/15ε always followed a proportionality near 1. Genome‐centred metagenomics revealed the enrichment of a few populations, such as Pseudomonas, Enterobacter, and Atlantibacter, most of which contained both NapA‐ and NarG‐type nitrate reductases. Metatranscriptome showed that both NapA and NarG were expressed but to different extents in the enrichments. Furthermore, isotopic data collected from a deep reservoir was analysed. The results showed δ18O‐ and δ15N‐nitrate did not correlate in the surface water where nitrification was active, but 18ε/15ε followed a proportionality of 1.05 ± 011 in deeper waters (≥ 12 m) where denitrification controlled the nitrate isotope. The independence of 18ε/15ε from carbon sources provides an opportunity to determine heterotrophic denitrification and helps the interpretation of nitrate isotopes in freshwaters. [ABSTRACT FROM AUTHOR]

Sulphur‐driven denitrification is a low‐cost process for the treatment of nitrate‐contaminated water. However, a comprehensive understanding of core populations and microbial interactions of a sulphur‐based denitrifying system is lacking. This study presents results from three replicated denitrifying systems amended with thiosulphate and operated under a low C/N ratio. Amplicon sequencing revealed gradual enrichments of a few abundant denitrifiers. Based on genome‐centred metagenomics and metatranscriptomics, a core set of microbes was identified in the systems, with Pseudomonas 1 and Thauera 2 being the most abundant ones. Although the replicates showed different enrichments, generalized observations were summarized. Most core populations conserved energy from denitrification coupled with sulphur. Pseudomonas 1 and Thauera 2 were able to finish complete denitrification. Surprisingly, they were also able to synthesize almost all amino acids and vitamins. In contrast, less abundant members, including Pseudomonas 2, were relatively auxotrophic and required an exogenous supply of amino acids and vitamins. The high expression of enzymes involved in biosynthesis and transport systems indicated their syntrophic relationships. The genomic findings suggested life strategies and interactions of the core thiosulphate‐based denitrifying microbiome, with implications for nitrate‐polluted water remediation. [ABSTRACT FROM AUTHOR]

Microbial nitrate reduction can be driven by organic carbon oxidation, as well as by inorganic electron donors, such as reduced forms of sulfur and iron. An apparent inverse oxygen isotope fractionation effect was observed during nitrate reduction in sediment incubations from five sampling sites of a freshwater lake, Hongze Lake, China. Incubations with organic and inorganic electron donor additions were performed. Especially, the inverse oxygen isotope effect was intensified after glucose addition, whereas the incubations with sulfide and Fe2+ showed normal fractionation factors. Nitrate reductase encoding genes, napA and narG, were analysed with metagenomics. Higher napA/narG ratios were associated with higher oxygen fractionation factors. The most abundant clade (59%) of NapA in the incubation with glucose was affiliated with Rhodocyclales. In contrast, it only accounted for 8%–9% of NapA in the incubations with sulfide and Fe2+. Differences in nitrate reductases might explain different oxygen isotope effects. Our findings also suggested that large variance of O‐nitrate isotope fractionations might have to be considered in the interpretation of natural isotope records. [ABSTRACT FROM AUTHOR]

Antibiotics are pollutants that are constantly discharged into ocean and coastal wetlands and affect the growth and activity of microorganisms. Ammonia‐oxidizing archaea (AOA) and bacteria (AOB), which are very important in the global nitrogen cycle, are affected by antibiotics in the environment as well. Antibiotics have different influences on AOA and AOB microbial communities due to their different biochemical compositions and metabolic mechanisms, which change the ammonia‐oxidizing process in different environments. In this study, 62 samples from four typical coastal wetland types along the Bohai Rim were collected and treated with streptomycin sulfate and penicillin in the laboratory. The total ammonia oxidation rate decreased by 61.2–84.0% with streptomycin sulfate and decreased by 50.0–74.5% with penicillin. The significant change in abundance and community structure indicated that AOB were more inhibited than AOA by streptomycin sulfate and penicillin. Nevertheless, ecological network analysis verified that the internal association in the AOA community was more fragile than that in the AOB community. Moreover, the relationship between AOA and other nitrogen‐transforming functional archaea weakened in the presence of antibiotics, while AOB established relationships with more nitrogen‐transforming functional bacteria in the presence of antibiotics. Streptomycin sulfate had a stronger effect than penicillin due to the different inhibiting mechanisms of these antibiotics and the promotion of interspecific cooperation induced by penicillin in AOA. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Treatment of super heavy oil wastewater (SHOW) is an increasing problem due to the large amounts of recalcitrant contaminants. Thus advanced techniques should be explored. RESULTS: A pilot field study was conducted by unsaturated ligntie‐activated coke (LAC) pre‐adsorption–immobilized biological filter (I‐BF) degradation–LAC post‐adsorption. Specially, the unsaturated LAC from the post‐adsorption stage was sent to the influent wastewater for pre‐adsorption. Through this novel process, the effluent can meet the prescribed discharge standard, and LAC dosage was significantly lower compared with the process without pre‐adsorption. Gas chromatography‐mass spectrometry (GC‐MS) demonstrated that pre‐adsorption could remove mostly organic substances which benefits the subsequent bio‐treatment; in particular, I‐BFs could remove phenols, organic acid compounds and light alkanes, whereas post‐adsorption preferentially removed amide. Liquid chromatography with organic carbon detection (LC‐OCD) indicated that pre‐adsorption could easily remove hydrophobic organic carbon (HOC), whereas I‐BFs and post‐adsorption principally removed neutrals. Thus, this process readily removes HOC, organic acids, biopolymers and neutrals, although humics (proven to be sewage fulvic acids) and building blocks are hard to remove. We also monitored the microbial community based on polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and revealed that the predominant bacteria in the I‐BF reactors were Bacteroides spp., Pseudomonas spp., Thermomonas spp., Sphingomonadaceae spp., Sphingomonas spp. and Rhizobium spp. CONCLUSION: This process provides an effective way for the treatment of SHOW. Results concerning the removal mechanism of recalcitrant contaminants and the in‐depth study of predominant bacteria may provide significant guidance for other wastewater treatments. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]