Dataset Information

Co-culturing Bacillus subtilis and wastewater microbial community in a bio-electrochemical system enhances denitrification and butyrate formation

ABSTRACT: 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.

ORGANISM(S): Clostridium beijerinckii Clostridium butyricum

PROVIDER: GSE150480 | GEO | 2020/05/15

REPOSITORIES: GEO

ACCESS DATA

Similar Datasets

Project description:Bioelectrochemical systems employing mixed microbial communities as biocatalysts are gaining importance as potential renewable energy, bioremediation, or biosensing devices. While we are beginning to understand how individual microorganism species interact with an electrode as electron donor, not much is known about the interactions between different microbial species in a community. Here, we compare the bioelectrochemical performance of Shewanella oneidensis in a pure-culture and in a co-culture with the homolactic acid fermenter Lactococcus lactis. While S. oneidensis alone can only use lactate as electron donor for current production, the co-culture is able to convert glucose into current with a similar coulombic efficiency of approximately 17%, respectively. With (electro)-chemical analysis and transcription profiling, we found that the BES performance and S. oneidensis physiology were not significantly different whether grown as a pure- or co-culture. These co-culture experiments represent a first step in understanding microbial interactions in BES communities with the goal to design complex microbial communities, which specifically convert target substrates into electricity. Further, for the first time, we elucidated S. oneidensis gene expression with an electrode as the only electron acceptor. The expression pattern confirms many previous studies regarding the enzymatic requirements for electrode respiration, and it generates new hypotheses on the functions of proteins, which are so far not known to be involved in electrode respiration. The BES was either operated with S. oneidensis alone, fed with lactate, or it was operated with S. oneidensis and L. lactis with glucose as primary substrate. The basic medium was a modified M4 medium containing 0.5 g/L yeast extract, 0.5 g/L trypton and 5 g/L glycerol phosphate, besides the commen M4 incredients. S. oneidensis oxidizes lactate to acetate and electrons in a BES - the latter generate a current at a graphite anode. The anode biofilm was harvested after about 4 weeks of continuous BES operation and subjected to total RNA extraction.

Project description:In comparison with provision of either ammonium or nitrate alone, simultaneously supplying both forms of N results in superior growth and yield for the majority of plants including rice. Using a rice 22K oligo-array, we performed transcriptome analysis to identify genes of rice (Oryza sativa L. ssp. japonica) responsive to change of N-supply forms and N-starvation. Using the supply of ammonium nitrate (one to one molar ratio) as control, the total number of root genes that were equal or more than two fold up- or down- regulated was 445, 324, and 781 by upon supply of either ammonium or nitrate or continuous N starvation, respectively for 96 h. In the shoot the equivalent numbers were much smaller only 32, 58, and 165, respectively. Clustering of the rice genes associated with different environmental stresses revealed substantial organ specificity of the root and shoot to N starvation, and also to the N supply form. Genes encoding transporters for ammonium and nitrate, nitrate reductase, glutamate dehydrogenase, and aspartate amino transferase, showed great response to change of the N supply form, especially to N starvation. Some of the genes involved in chlorophyll metabolism, carbon fixation and assimilation, were enhanced by ammonium supply only, but significantly suppressed by N-starvation. In the shoot there was increased expression of more general stress genes under nitrate when compared to ammonium nutrition. In the root the reverse situation was true with more apparent stress under ammonium nutrition. The microarray approach has revealed new levels of complexity in the response of rice to the form of N supply. Experiment Overall Design: Rice seedlings were grown in a hydroponic system in a growth chamber with control of both temperature and light. After normal growth for two weeks and for one week with completely avoiding any N source, the plants at four and a half leaf stage were re-supplied with ammonium nitrate (equal amount of either form of N), or only ammonium (ammonium sulphate and ammonium chloride), or only nitrate (calcium nitrate and magnesium nitrate), and continuing at zero N (N starvation). All the other essential nutrients were the same for all four treatments, except for sulfate and chloride which ranged between 1.1 â 2.6 mM and 0.5 â 2.5 mM, respectively. In Arabidopsis, addition of 3 mM Cl to âcontrolsâ did not produce any changes in the expression of genes in an experiment investigating the re-supply of 3 mM nitrate (Scheible et al., 2004). In other microarray experiments, extra addition of 5 mM Cl for Arabidopsis (Wang et al., 2000; Wang et al., 2004) and 1.4 mM sulphate for tomato (Wang et al., 2001) were used to replace nitrate for identifying the N deprivation responsive genes. Therefore, we assume that the relative smaller difference in sulfate and chloride concentrations among the four treatments in the normal supply range for plants would not significantly affect the expression profile of genes responsible for changes in N supply form and starvation in our experiments. Experiment Overall Design: For identifying the genes responding to the various N conditions by micro-array analysis, we extracted total RNA respectively from the roots and shoots at the 96 h after initiation of the four respective treatments. We used amplified and labeled cRNA from ammonium nitrate treatment as control, we performed array-hybridization for the cRNA from the treatment of single ammonium form, single nitrate form, or continuous N depletion, respectively. Agilent 60-mer oligonucleotide arrays containing 21,938 unique transcription units (Agilent Technologies, Tokyo, Japan) were used. Two biological replicates of each treatment were performed for microarray analyses.

Dataset Information

Co-culturing Bacillus subtilis and wastewater microbial community in a bio-electrochemical system enhances denitrification and butyrate formation

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure