Project description:Acididesulfobacillus acetoxydans is an acidophilic sulfate reducer that can dissimilatory reduce nitrate to ammonia (DNRA). However, no known nitrite reductase is encoded. This study was performed to investigate how A. acetoxydans reduces nitrate to nitrite and elucidated a novel DNRA mechanism and potential nitrosative stress resistance mechanisms in acidophiles.
Project description:Dissimilatory nitrate reduction to ammonia (DNRA) is an important part of the microbial N-cycle both in natural and man-made habitats, although its significance in wastewater treatment plants is not well understood. Nitrate-limited enrichments from activated sludge with acetate as e-donor consistently resulted in a domination of two closely related genotypes of ammonifying members of Deltaproteobacteria belonging to the genus Geobacter. One of the two was isolated in pure culture which appears to be an extremely specialized ammonifier, actively growing only with acetate as e-donor and C source and nitrate as e-acceptor. The shotgun proteomic raw data obtained from whole cell lysates are provided. First and corresponding author: Dimitry Y. Sorokin soroc@inmi.ru; d.sorokin@tudelft.nl
Project description:Geobacter sulfurreducens is a widely explored microorganism recognized by its metabolic versatility able to reduce a number of external electron acceptors. In the present study the capacity of this strain to reduce nitrate was evaluated along with its transcriptomic profile under nitrate-reducing conditions and the catalytic role of Pd nanoparticles on the reductive pathway. Results demonstrated that G. sulfurreducens was able to reduce nitrate and important kinetic differences related to the time response were found among the electron donors used (acetate and hydrogen). When using acetate, a delay response on nitrate reduction of 4 days and reduction of 94% of nitrate was achieved, while nitrite was not detected, and all the nitrogen was recovered as ammonium (79.6 ± 5.7 %). The use of hydrogen as electron donor increased 2-fold the maximum rate of nitrate reduction, leading to 93% reduction of nitrate during the first 20 h with recovery of 45% as ammonium, while nitrite was not detected. In addition, transcriptome profiling analysis of G. sulfurreducens under nitrate-reducing conditions using hydrogen or acetate as an electron donor at 2 and 6 days reveals that a core of 146 genes (69 upregulated and 77 downregulated) are differentially expressed in all conditions. Genes related to nitrogen metabolism, such as nrfA and nrfH, gdhA, and amtB, were upregulated in the incubations and RT-qPCR data confirmed upregulations of these genes. Experiments performed with biologically synthesized Pd (Bio-Pd) + G. sulfurreducens cells demonstrated synergistic input of Bio-Pd and the metabolic capacity of G. sulfurreducens. These results expand the metabolic versatility of G. sulfurreducens, which may have important implications in nitrogen cycling in natural environments and engineered systems.
Project description:Bio-augmentation could be a promising strategy to improve processes for treatment and resource recovery from wastewater. In this study, the Gram-positive bacterium Bacillus subtilis was co-cultured with the microbial communities present in wastewater samples with high concentrations of nitrate or ammonium. Glucose supplementation (1%) was used to boost biomass growth in all wastewater samples. In anaerobic conditions, the indigenous microbial community bio-augmented with B. subtilis was able to rapidly remove nitrate from wastewater. In these conditions, B. subtilis overexpressed nitrogen assimilatory and respiratory genes including NasD, NasE, NarG, NarH, and NarI, which arguably accounted for the observed boost in denitrification. Next, we attempted to use the the ammonium- and nitrate-enriched wastewater samples bio-augmented with B. subtilis in the cathodic compartment of bioelectrochemical systems (BES) operated in anaerobic condition. B. subtilis only had low relative abundance in the microbial community, but bio-augmentation promoted the growth of Clostridium butyricum and C. beijerinckii, which became the dominant species. Both bio-augmentation with B. subtilis and electrical current from the cathode in the BES promoted butyrate production during fermentation of glucose. A concentration of 3.4 g/L butyrate was reached with a combination of cathodic current and bio-augmentation in ammonium-enriched wastewater. With nitrate-enriched wastewater, the BES effectively removed nitrate reaching 3.2 mg/L after 48 h. In addition, 3.9 g/L butyrate was produced. We propose that bio-augmentation of wastewater with B. subtilis in combination with bioelectrochemical processes could both boost denitrification in nitrate-containing wastewater and enable commercial production of butyrate from carbohydrate- containing wastewater, e.g. dairy industry discharges. These results suggest that B. subtilis bio-augmentation in our BES promotes simultaneous wastewater treatment and butyrate production.
2020-05-15 | GSE150480 | GEO
Project description:DNRA nrfA genes
| PRJNA597679 | ENA
Project description:Physiology of dissimilatory nitrate reduction to ammonium (DNRA) in rice paddy soil isolates acquired with a newly developed high-throughput screening method
Project description:The conversion of nitrate to ammonium, known as nitrate reduction, consumes large amounts of reductants in plants. Previous studies have observed that mitochondrial alternative oxidase (AOX) is upregulated under conditions of limited nitrate reduction, such as low or no nitrate availability, or when ammonium serves as the sole nitrogen (N) source. Electron transfer from ubiquinone to AOX bypasses the proton-pumping complexes III and IV, thereby consuming reductants efficiently. Therefore, the upregulation of AOX under conditions of limited nitrate reduction may help dissipate excessive reductants and mitigate oxidative stress. However, firm evidence supporting this hypothesis is lacking due to the absence of experimental systems capable of directly analyzing the relationship between nitrate reduction and AOX. To address this gap, we developed a novel culturing system that allows for the manipulation of nitrate reduction and AOX activities separately, without inducing N starvation, ammonium toxicity, or disrupting the nitrate signal. Using this system, we investigated genome-wide gene expression with RNA-seq to gain insight into the relationship between AOX and nitrate reduction.
Project description:Shewanella algae C6G3 can conduct dissimilative nitrate reduction into ammonium and MnIV reduction. This bacteria have the unusual ability to produce anaerobically nitrite from ammonium in the presence of MnIV. This property may explain NO2/3- accumulation observed in some anaerobic zones of marine sediments. To gain insight into their metabolic capabilities, global mRNA expression patterns were investigated by RNA-seq and qRT-PCR in cells growing with lactate and ammonium as carbon and nitrogen sources and with MnIV or nitrate as electron acceptors. Genes exhibiting higher expression levels in the presence of MnIV belonged to functional categories of carbohydrate, coenzyme, lipid metabolisms and inorganic ion transport. Furthermore, comparative transcriptomic pattern between MnIV and NO3 revealed that the strain presented an ammonium limitation status with MnIV, despite the presence of identical and non-limiting concentration of ammonium in both culture conditions. Regulators ntrB/nrtC, ammonium channel, nitrogen regulatory protein P-II, glutamine synthetase and asparagine synthetase glutamine dependent genes were over-expressed. In nitrate condition, genes involved in synthesis of several amino acids were over expressed. Among the genes associated with the stress response, Kat E was highly expressed particularly under manganese condition
Project description:Reforestation is effective in restoring ecosystem functions and enhancing ecosystem services of degraded land. The three most commonly employed reforestation methods of natural reforestation, artificial reforestation with native Masson pine (Pinus massoniana Lamb.), and introduced slash pine (Pinus elliottii Engelm.) plantations were equally successful in biomass yield in southern China. However, it is not known if soil ecosystem functions, such as nitrogen (N) cycling, are also successfully restored. Here, we employed a functional microarray to illustrate soil N cycling. The composition and interactions of N-cycling genes in soils varied significantly with reforestation method. Natural reforestation had more superior organization of N-cycling genes, and higher functional potential (abundance of ammonification, denitrification, assimilatory, and dissimilatory nitrate reduction to ammonium genes) in soils, providing molecular insight into the effects of reforestation.