Project description:Anaerobic ammonium-oxidising (anammox) bacteria, members of the ‘Candidatus Brocadiaceae’ family, play an important role in the nitrogen cycle and are estimated to be responsible for about half of the oceanic nitrogen loss to the atmosphere. Anammox bacteria combine ammonium with nitrite and produce dinitrogen gas via the intermediates nitric oxide and hydrazine (anammox reaction) while nitrate is formed as a by-product. These reactions take place in a specialized, membrane-bound compartment called the anammoxosome. Therefore, the substrates ammonium, nitrite and product nitrate have to cross the outer-, cytoplasmic- and anammoxosome membranes to enter or exit the anammoxosome. The genomes of all anammox species harbour multiple copies of ammonium-, nitrite- and nitrate transporter genes. Here we investigated how the distinct genes for ammonium-, nitrite- and nitrate- transport were expressed during substrate limitation in membrane bioreactors. Transcriptome analysis of Kuenenia stuttgartiensis planktonic cells under ammonium-limitation showed that three of the seven ammonium transporter genes and one of the six nitrite transporter genes were significantly upregulated, while another ammonium and nitrite transporter gene were downregulated in nitrite limited growth conditions. The two nitrate transporters were expressed to similar levels in both conditions. In addition, genes encoding enzymes involved in the anammox reaction were differentially expressed, with those using nitrite as a substrate being upregulated under nitrite limited growth and those using ammonium as a substrate being upregulated during ammonium limitation. Taken together, these results give a first insight in the potential role of the multiple nutrient transporters in regulating transport of substrates and products in and out of the compartmentalized anammox cell.
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.
Project description:Central nervous system (CNS) injuries and neurodegenerative diseases have markedly poor prognoses and can result in permanent dysfunction due to the general inability of CNS neurons to regenerate. Differentiation of transplanted stem cells has emerged as a therapeutic avenue to regenerate tissue architecture in damaged areas. Electrical stimulation is a promising approach for directing the differentiation outcomes and pattern of outgrowth of transplanted stem cells, however traditional inorganic bio-electrodes can induce adverse effects such as inflammation. Here, we demonstrate the implementation of two organic thin films, a polymer/reduced graphene oxide nanocomposite (P(rGO)) and PEDOT:PSS, that have favorable properties for implementation as conductive materials for electrical stimulation, as well as an inorganic indium tin oxide (ITO) conductive film. Transcriptomic analysis revealed that electrical stimulation improved neuronal differentiation of SH-SY5Y cells on all three films, with the greatest effect for P(rGO). Unique material- and electrical stimuli-mediated effects were observed, associated with differentiation, cell-substrate adhesion, and translation. Our work demonstrates that P(rGO) and PEDOT:PSS are highly promising organic materials for the development of biocompatible, conductive scaffolds that will enhance electrically-aided stem cell therapeutics for CNS injuries and neurodegenerative diseases.
Project description:The bacteria that grow on methane aerobically (methanotrophs) support populations of non-methanotrophs in the natural environment by excreting methane-derived carbon. One group of excreted compounds are short-chain organic acids, generated in highest abundance when cultures are grown under O2-starvation. We examined this O2-starvation condition in the methanotroph Methylomicrobium buryatense 5GB1C . Under prolonged O2-starvation in a closed vial, this methanotroph increases the amount of acetate excreted about 10-fold, but the formate, lactate, and succinate excreted do not respond to this culture condition. In bioreactor cultures, the amount of each excreted product is similar across a range of growth rates and limiting substrates, including O2-limitation. A set of mutants were generated in genes predicted to be involved in generating or regulating excretion of these compounds and tested for growth defects, and changes in excretion products. The phenotypes and associated metabolic flux modeling suggested that in M. buryatense 5GB1C, formate and acetate are excreted in response to redox imbalance, and the resulting metabolic state represents a combination of fermentation and respiration metabolism.
Project description:In this study, we investigated Mn3+-cycling microbial populations enriched from Lake Matano, Indonesia using metagenomics and metaproteomics. Lake Matano contains an active Mn cycle that links the oxic-anoxic interface with anoxic deep waters that are enriched in iron and manganese, and depleted in sulfate, phosphate, and oxidized nitrogen (Crowe et al., 2008; Jones et al., 2011). Sediments were incubated with sequential transfers for ~1 year with Mn3+ as the sole electron acceptor and methane as organic carbon until achieving sediment-free conditions. Here we investigate this novel species of Dechloromonas (Betaproteobacteria), “Candidatus Dechloromonas occultata,” which was the dominant population in enrichment cultures with active Mn3+ reduction. “Ca. D. occultata” expressed electron conduits related to those involved in Fe2+ oxidation (Mto-like), as well as a novel cytochrome c-rich gene cluster putatively involved in extracellular electron transfer, and an atypical nitrous oxide reductase. According to ribosomal counts, Dechloromonas outnumber Geobacter. In terms of functional genes, Dechloromonas expresses a wider variety and number of genes. Dechloromonas therefore seems to have a (selective?) advantage over Geobacter. Previous experiments revealed that Dechloromonas express nitrogen regulators, reductases and scavenging genes, as well as many carbon central metabolic pathways, and aromatic carbon degradation pathways. Dechloromonas is a beta proteobacteria, and these are "experts" in nitrogen metabolism. Geobacter, on the other hand, is well known for carbon degradation. Our previous experiments lead to our hypothesis that Dechloromonas is more active because they are more successful at acquiring nitrogen, a limiting nutrient for Geobacter. This would further suggest that carbon is not the limiting nutrient. We will test 2 hypotheses with the next suite of experiments 1) pyrophosphate supports the community, by allowing carbon fixation , 2)Dechloromonas has a (selective?) advantage over Geobacter. To test this hypothesis, bioreactors will be used to grow biotriplicate cultures of (1)- CH4 vs. pyrophosphate and (2)-CH4 vs. Mn(III) pyrophosphate. Here we have analyzed whole cell pellets using gas phase fractionations on the Q Exactive. Are Dechloromonas capable of out-competing Geobacter when grown in media with methane as the only carbon source bioreactors because they are capable of acquiring more nitrogen? Source of inoculum. Lake Matano is a metal-rich, ancient ocean analog (Crowe et al. 2011, Jones et al. 2011). Organic carbon in Lake Matano is mostly mineralized via methanogenesis before reaching the iron-rich sediments, limiting organic matter bioavailability for metal-reducers (Kuntz et al. 2015). A 15-cm sediment core from 200 m water depth in Lake Matano, Sulawesi Island, Indonesia (02°26′27.1′′S, 121°15′12.3′′E; in situ sediment temperature ~27°C) was sampled in November 2014 and sub-sampled at 5 cm increments. Sediments were sealed in gas-tight Mylar bags with no headspace (Hansen et al. 2000) and stored at 4°C until incubations began in December 2015.
Project description:We integrated genomic and transcriptomic analysis of a newly isolated obligate Methylomonas sp. DH-1 grown on methane and methanol. Comparative transcriptomic analysis between methane and methanol as a sole carbon source revealed different transcriptional responses of Methylomonas sp. DH-1, especially in C1 assimilation, the secondary metabolites pathways and the oxidative stress related genes
2019-02-26 | GSE101494 | GEO
Project description:stable anammox under limited ammonium condition