1,720,995 research outputs found
The degradation of glyphosate is enhanced in a microbial fuel cell: Electrochemical performance, degradation efficiency, and analysis of the anodic microbial community
Get PDFGlyphosate, one of the most used herbicides worldwide, is known as an aquatic contaminant of concern, and has been identified as presenting adverse impacts in agroecosystems, due to a somewhat limited natural chemical and biological degradation in the environment. In this study, we investigated the degradation of glyphosate in microbial electrochemical systems (MESs), and compared the performance and the microbial composition of enriched anodic biofilms with those shown by native microbial communities. The reduction of glyphosate content observed in MESs (approx. 70 %) was much higher than in non-electroactive microbial cultures (approx. 49 %). The analysis of the microbial communities by 16S amplicon sequencing revealed a significant difference between the microbial community composition of MESs anodic biofilms and non-electroactive enriched communities. The anodic biofilms were dominated by Rhodococcus (51.26 %), Pseudomonas (10.77 %), and Geobacter (8.67 %) while in non-MESs cultures, methanogens including Methanobrevibacter (51.18 %), and Methanobacterium (10.32 %), were the dominant genera. The present study suggested that MESs could be considered as a promising system for complete degradation of glyphosate from waters polluted by this herbicide
Generating electricity with urban green infrastructure microbial fuel cells
Get PDFUrban areas can modify their green infrastructure to include microbial fuel cells and generate electricity to help address energy security. Naturally occurring electroactive bacteria utilize plant compounds and organic pollutants as electron donors. Water is cleaned, electricity is generated, and additional ecological services are provided
A Computational Study of the Role of Nuclear Receptor Interactions in Steatosis
Get PDFIt is estimated that 1 in 3 people in the UK show early warning signs of Non-Alcoholic Fatty Liver Disease (NAFLD), a condition that starts with steatosis, the abnormal accumulation of lipid cells in the liver. Understanding the processes by which this accumulation of lipids occurs could lead to the development of novel drugs to treat steatosis before disease progression can occur. A systems wide computational approach was adopted to understand the interaction between metabolism, cell signalling and gene regulation producing a phenotypic output that resembles steatosis. The in silico model comprises of two different computational formalisms: the human Genome-Scale Metabolic Network (GSMN) Recon2 (analysed using Flux Balance Analysis (FBA)), coupled with the MAP Kinase signalling network; and Nuclear Receptor (NR) gene regulation modelled using Petri Net (PN) theory. These two distinct formalisms are combined using the Quasi-Steady State Petri Net (QSSPN) algorithm. Previously published work uses small-scale static models. This project builds on that research by using quantitative data for the dynamic gene regulatory network, including experimentally determined reaction rates, protein levels and receptor occupancy levels. It also includes the MAP Kinase signalling network created by the conversion of the Reactome dataset, and comprises six MAPK-activated NRs. The results showed that the model can uncover previously unknown metabolic landscapes. It was found that Glucocorticoid Receptor (GR) has an inhibitory effect when coupled with any other NR (excluding the Peroxisome-Proliferator Activated Receptor Alpha (PPARa)), which causes a decrease in the synthesis of triacylglycerol (TAG). This was due to GRs inhibition of IDH1, a gene that upregulates the enzyme isocitrate dehydrogenase. PPARa had a neutralising effect when combined with GR, sustaining a steady state level of TAG. In conclusion, the dynamic mechanistic model developed has the capability to study the metabolic network on a system wide level and identify new biological mechanisms. Supporting data can be found at http://doi.org/10.15126/surreydata.0085823
Efecto de distintas condiciones de cultivo sobre la toxicidad y esporulación de Bacillus thuringiensis var. Israelensis
Get PDFA partir de los resultados presentados en este trabajo de Tesis se pueden extraer conclusiones que contribuirán a alcanzar un conocimiento más acabado de la microbiología y de la tecnología de cultivo de Bacillus íhuringiensis var. is rae l ensis.
La necesidad de emplear medios complejos para cultivar Bacillus íhuringiensis var. israelensis queda demostrada mediante los experimentos realizados empleando medios sintéticos (Capítulo 2). El desarrollo del microorganismo en estos medios es lento, y no es posible reemplazar la fuente de nitrógeno compleja por vitaminas y aminoácidos. También se demostró que los medios deben ser suplementados con amonio, con lo que se obtiene un aumento significativo en la producción de proteína tóxica.
Los experimentos en tanques agitados (Capítulo 3) permitieron determinar los parámetros de crecimiento del microorganismo, algunos de los cuales mostraron buena concordancia con datos de la literatura para otras variedades de Bacillus íhuringiensis. Es posible emplear medios concentrados (siete veces la concentración del medio de referencia), observándose una cierta inhibición en el crecimiento. Medios de mayor concentración causan una mayor inhibición, con supresión de la esporulación y sin producción de toxina. Este efecto puede revertirse diluyendo los cultivos.
La aireación y la agitación afecta de modo sensible el crecimiento, la esporulación y la producción de toxina de Bacillus íhuringiensis var. israelensis (Capítulo 4). Se verifican variaciones importantes en los rendimientos cuando se estudian cultivos limitados y no limitados por oxígeno. La interrupción de la aireación provoca la supresión de la síntesis de toxina.
Los ensayos realizados en batch alimentado con distintas estrategias de alimentación (Capítulo 5) permiten ver que las condiciones iniciales del cultivo afectan la estabilidad del sistema de modo muy marcado. Asimismo, los cultivos alimentados con perfiles exponenciales muestran acumulación de glucosa, con lo que el control de la velocidad de crecimiento se imposibilita.
El consumo de nitrógeno en los cultivos lineales muestra diferencias respecto de los cultivos en batch. Los cultivos exponenciales indican que a mayor velocidad de alimentación, menor consumo de amonio.
La toxicidad alcanzada en los cultivos batch alimentado, cualquiera sea el perfil de alimentación, son un orden de magnitud menores que la alcanzada en cultivos batch. El perfil de polipéptidos componentes de los cristales con menor toxicidad presenta una banda de 20 kDa, que no se observa en los cristales obtenidos en cultivos batch.
Cuando se realiza el análisis estequiométrico de los cultivos (Capítulo 6) se observa que los cultivos batch y batch alimentado exponencial con velocidades de alimentación cercanas al µmax presentan acumulación de ácido acético. Los cultivos alimentados exponenciales a menores valores de µ no presentan acumulación de ácido. Esta podría deberse a la sobreoferta de fuente de carbono y energía que se observa en los cultivos realizados a altos valores de µ.Tesis digitalizada en SEDICI gracias a la Biblioteca Central de la Facultad de Ciencias Exactas (UNLP).Doctor en Ciencias BioquímicasUniversidad Nacional de La PlataFacultad de Ciencias Exacta
Efecto de distintas condiciones de cultivo sobre la toxicidad y esporulación de Bacillus thuringiensis var. Israelensis
Get PDFA partir de los resultados presentados en este trabajo de Tesis se pueden extraer conclusiones que contribuirán a alcanzar un conocimiento más acabado de la microbiología y de la tecnología de cultivo de Bacillus íhuringiensis var. is rae l ensis.
La necesidad de emplear medios complejos para cultivar Bacillus íhuringiensis var. israelensis queda demostrada mediante los experimentos realizados empleando medios sintéticos (Capítulo 2). El desarrollo del microorganismo en estos medios es lento, y no es posible reemplazar la fuente de nitrógeno compleja por vitaminas y aminoácidos. También se demostró que los medios deben ser suplementados con amonio, con lo que se obtiene un aumento significativo en la producción de proteína tóxica.
Los experimentos en tanques agitados (Capítulo 3) permitieron determinar los parámetros de crecimiento del microorganismo, algunos de los cuales mostraron buena concordancia con datos de la literatura para otras variedades de Bacillus íhuringiensis. Es posible emplear medios concentrados (siete veces la concentración del medio de referencia), observándose una cierta inhibición en el crecimiento. Medios de mayor concentración causan una mayor inhibición, con supresión de la esporulación y sin producción de toxina. Este efecto puede revertirse diluyendo los cultivos.
La aireación y la agitación afecta de modo sensible el crecimiento, la esporulación y la producción de toxina de Bacillus íhuringiensis var. israelensis (Capítulo 4). Se verifican variaciones importantes en los rendimientos cuando se estudian cultivos limitados y no limitados por oxígeno. La interrupción de la aireación provoca la supresión de la síntesis de toxina.
Los ensayos realizados en batch alimentado con distintas estrategias de alimentación (Capítulo 5) permiten ver que las condiciones iniciales del cultivo afectan la estabilidad del sistema de modo muy marcado. Asimismo, los cultivos alimentados con perfiles exponenciales muestran acumulación de glucosa, con lo que el control de la velocidad de crecimiento se imposibilita.
El consumo de nitrógeno en los cultivos lineales muestra diferencias respecto de los cultivos en batch. Los cultivos exponenciales indican que a mayor velocidad de alimentación, menor consumo de amonio.
La toxicidad alcanzada en los cultivos batch alimentado, cualquiera sea el perfil de alimentación, son un orden de magnitud menores que la alcanzada en cultivos batch. El perfil de polipéptidos componentes de los cristales con menor toxicidad presenta una banda de 20 kDa, que no se observa en los cristales obtenidos en cultivos batch.
Cuando se realiza el análisis estequiométrico de los cultivos (Capítulo 6) se observa que los cultivos batch y batch alimentado exponencial con velocidades de alimentación cercanas al µmax presentan acumulación de ácido acético. Los cultivos alimentados exponenciales a menores valores de µ no presentan acumulación de ácido. Esta podría deberse a la sobreoferta de fuente de carbono y energía que se observa en los cultivos realizados a altos valores de µ.Tesis digitalizada en SEDICI gracias a la Biblioteca Central de la Facultad de Ciencias Exactas (UNLP).Doctor en Ciencias BioquímicasUniversidad Nacional de La PlataFacultad de Ciencias Exacta
Invasion of pseudomonas aeruginosa populations through the altered expression of pyoverdine primary and secondary receptors
Get PDF‘Evolutionary medicine’ has been proposed as an alternative treatment of infectious diseases in response to the emergence of multidrug resistant bacterial pathogens and to the limited availability of new antibiotics. Among potential treatments, microbial “Trojan horses” are a way of deploying weaknesses in microbial populations by invading them with tailor-made bacteria (e.g. sensitive to antibiotics). Here I exploit the fitness cost linked to the production of the siderophore pyoverdine in the human pathogen Pseudomonas aeruginosa for population invasion. Individuals in a population that do not produce the siderophore do not pay the cost and can overtake a population. However, cooperative individuals are preserved by the presence of structure in the population (e.g. growth in biofilms) that limits the diffusion of pyoverdine, therefore preventing the invasion by non-cooperators. I overcame this limitation by altering the individual benefit acquisition through the deletion and/or overexpression of pyoverdine primary (FpvA) and secondary receptors (FpvB). I characterised growth and pyoverdine production strategies in iron limited conditions in a variety of scenarios in both monocultures and competition experiments against the wildtype MPAO1. My results show that the selective manipulation of pyoverdine receptors leads to different evolutionary dynamics in the population, which are dependent on the relationship between costs of pyoverdine production and benefits of reception during balanced growth, as well as in the kinetics of this process prior to exponential growth. These strategies change in response to environmental inputs such as the presence of a stressor and are maintained when cells grow in biofilms and during infections of Galleria mellonella, both of which are representative of structured environments. By interfering with the complex regulatory network of pyoverdine production and reception, I produced strains with optimised investments under certain conditions that successfully displace a wildtype population therefore paving the way for their use as ‘Trojan horses’ for population control
The application of radiation-grafted ion-exchange membranes in microbial fuel cells.
Get PDFThis project will look at the application and development of radiation-grafted ion-exchange membranes in a microbial fuel cells. An aim is to develop low resistance ion-exchange membranes (IEMs) that do not have increased O2 crossover.
It has previously been found that the use of anion exchange membranes (AEMs) may improve the performance of microbial fuel cells. The literature suggests that the use of AEMs over cation-exchange membranes (CEMs) might give a more favourable power output. However, the radiation grafted (RG) AEMs tested in this study displayed a poorer performance both in situ and ex situ than the industry standard CEM (Nafion® 115). Lower MFC power density (ca. 8 mW m-2 for the RG-AEM compared to ca 10 mW m-2 for Nafion® 115) and lower conductivity (0.007 S cm-2 compared to 0.032 S cm-2) were both observed. An RG-CEM with the same base polymer as a previously tested RG-AEM was also produced. Comparisons between the MFC performance of the RG-CEM and Nafion® were more favourable, showing higher voltage output and lower O2 permeability.
The results of an oxygen permeability test suggest that both the RG-AEMs and RG-CEMs exhibit a lower oxygen crossover, which is preferable when looking at MFC applications. However, the RG-AEM conductivities were lower than the RG-CEM and Nafion®. Despite this, the conductivities of the RG-AEMs were less affected when in contact with solutions containing buffer and bacteria.
A recommendation for future work is to explore more widely the use of RG-CEM in MFCs
Metabolic analysis of solventogenic clostridium saccharoperbutylacetonicum N1-4 (HMT).
Get PDFThe market for solvent production is predicted to reach $43.4 billion in 2018, with n-butanol having over 20% market share value where n-Butanol is the chemical precursor of several industrially important products, such as butyl-acetate, butyl-acrylate, glycol-ethers, and plasticisers. Butanol is currently produced from crude oil, and therefore in light of dwindling fossil fuel reserves, and more importantly, the need for green and clean production processes, synthesis of bio-butanol from biomass using Clostridia represents a viable and desirable alternative method.
This project focuses on the metabolic and physiologic characterisation of the acetone-butanol-ethanol (ABE) producing species Clostridium saccharoperbutylacetonicum (Csb). A minimal medium for Csb was defined based on literature data, modified by the addition of glutamate to support growth. Interestingly, batch cultures using this medium showed that Csb was able to grow and produce butanol under aerobic conditions, with titres of approximately 74% of those observed under anaerobic conditions.
Steady state cultures in chemostats are essential to elucidate and characterise physiological features of microorganisms. Steady state cultures of Csb were used to determine the effect of acid production on solventogenesis, bacterial growth, and energy metabolism. Studies at different pH in the range 5.5 to 6.5 showed no correlation with the onset of solventogenesis. However, the pH and the growth rate seem to influence the productivity of butanol. In those experiments, significant increases in the production rate of butanol were observed when the dilution (growth) rate increased from 0.01 h-1 to 0.03 h-1 and the pH decreased from 6.5 to 5.5. Growth is potentially linked to production rate due to an increased demand for ATP and NADH recycling.
The use of genome scale metabolic models allows for the interpretation of metabolic and physiological changes upon changes in the culture conditions. A metabolic model of Csb was constructed based on the genome sequence of the microorganism and incorporating biomass synthesis equations specific for Csb which were constructed based on the analysis of the composition of the cells grown in the chemostat experiments, as opposed to current models that use biomass composition from related species (e.g. B. subtilis).
The metabolic model was used to perform flux balance analysis to identify and interpret the changes in the distribution of metabolic fluxes that would explain the metabolic changes observed in Csb cultured under different conditions.
This work has demonstrated the basis for the presence of monophasic solventogenesis in C. saccharoperbutylacetonicum and provided important tools (defined media, GSMN equations) to improve industrial scale production of renewable sources of carbon-based feedstocks and thus reducing reliance on crude oil.</p
δ-endotoxin activity and spore production in batch and fed-batch cultures of <i>Bacillus thuringiensis</i>
Get PDFThe toxicity and the spore count of batch and fed batch cultures of Bacillus thuringiensis var. israelensis were studied. Spore counts reached in both batch and fed batch cultures were as high as those reported in the literature, but the levels of toxicity found in the latter were about one order of magnitude lower than those attained in batch cultures. Avoiding restricted cultures might be necessary to reach high titres of δ-endotoxin, which are essential if a good product is intended. Furthermore, spore count might not be a good parameter to predict insecticidal activity of Bacillus thuringiensis cultures.Centro de Investigación y Desarrollo en Fermentaciones Industriale
Analysis of glucose carbon fluxes in continuous cultures of Bacillus thuringiensis
Get PDFThe glucose carbon fluxes in continuous cultures of Bacillus thuringiensis grown in a complex medium have been studied as a function of the growth rate. The results are discussed in the light of a growth model. From reduced nicotinamide adenine dinucleotide (NADH) and carbon balances it was determined that the fraction of glucose consumed for biomass synthesis decreased with the growth rate, while the glucose flux through the tricarboxylic acid (TCA) cycle diminished after a threshold value of D=0.34 h-1, where D=dilution rate. At the highest growth rate tested, glucose was used almost exclusively as the energy source, via fermentative pathways, which indicates that the yeast extract was used as the carbon source. The specific rate of oxygen consumption increased with growth even after the beginning of the accumulation of acids, indicating that the respiratory chain was not saturated. The results suggest that there is a mismatch between glycolysis and TCA cycle capacity, depending on the growth rate. Furthermore, values of (P/O) ratio and mATP are presented, where (P/O) is mole of ATP formed per gram atom oxygen consumed by the respiratory chains and mATP is the maintenance requirement for ATP.Centro de Investigación y Desarrollo en Fermentaciones Industriale
- …
