Difference between revisions of "Team:Westminster/Description"

 
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<I> Shewanella oneidensis </I> MR-1 is an important microorganism in bioremediation due to its diverse respiratory capabilities. It is a dissmilatory metal reducing bacterium. Being facultative organism, it has the ability to adapt the both aerobic and anaerobic environments as well as utilise a number of toxic compounds such as manganese and uranium. It does this by accepting electrons, which enables Shewanella oneidensis to have the potential to produce electricity. It is a specific pathway, known as the <I> Mtr </I> pathway which is involved in the accepting of electrons which then carries a potential electrical charge.
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<i>Shewanella oneidensis</i> MR-1 is an important microorganism in bioremediation due to its diverse respiratory capabilities. It is a dissmilatory metal reducing bacterium. Being facultative organism, it has the ability to adapt to both aerobic and anaerobic environments, as well as utilise a number of toxic compounds such as manganese and uranium. It does this by accepting electrons, which gives <i>Shewanella oneidensis</i> the potential of producing electricity. An electron transfer pathway, known as the <i>Mtr</i> pathway, facilitates the extracellular translocation of electrons that are gained during the reduction of a carbon source. <br><br>
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The Mtr pathway consists of the following five genes:
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The Mtr pathway consists of the following five genes:<br>
  
  
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2015 Westminster iGEM team have been working on introducing the Mtr pathway into <I> Escherichia coli</I>, in order to produce a microbial fuel cell (MFC) capable of producing electricity. The efficiency of the MFC is down to the biofilm which is formed when cells adhere to a surface and stick to each other, the composition of these biofilms is what determines the amount of electricity produced as it acts like a conductive matrix enabling higher kinetics rates of electron transfer along nanowires.
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We have been working on introducing the Mtr pathway into <i>Escherichia coli</i>, in order to increase the electrical output in a microbial fuel cell (MFC). <i>Shewanella oneidensis</i> is capable of transferring these electrons through extensions known as nanowires. However, <i>E.col</i> have a far greater genetic tool set at their disposal, enabling easy genetic manipulation and modification. Further more, they are a very robust microorganism that, when compared to <i>Shewanella oneidensis</i>, are better equipped to deal with changes in a range of environmental variables, e.g. temperature and pH. The carbon source for our modified bacteria will be wastewater.<br><br>
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By introducing this pathway into <I> E.coli</I>, we hope to increase the transfer of electrons and thus level of electricity produced. <I> Shewanella oneidensis </I> is capable of transferring these electrons through extensions known as nanowires. We are exploring the possibility of electron transfer through the use of flagella found in <I> E.coli </I> K-12 derivative, DH5-&alpha;. <I> E.coli </I> will act as an anode, using wastewater as its carbon source. Hence purifying the water in which the cathode will be found.
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We are exploring the possibility of electron transfer through the use of flagella found in <i>E.coli</i> K-12 derivative, DH5-α. <i>E.coli</i> should act as an anode. Formation of biofilm has also been noted in this strain of <i>E.coli</i>. The efficiency of the MFC is down to the biofilm, which is formed when cells adhere to a surface and stick to each other. The composition of these biofilms is what determines the amount of electricity produced as it acts like a conductive matrix, enabling higher kinetics rates of electron transfer along nanowires. <br><br>
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This technology has wide reaching global implications such as wastewater treatment to produce electricity and clean water, which could be beneficial to developed and undeveloped countries alike. They could also be used as an electrical source for deep water biosensors within a sediment microbial fuel cell. Furthermore they could play a major role in bioremediation, which is removal of organic pollutants from environments to produce clean water and excess electrical energy.
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This technology has a multitude of application. It could be used as an electrical source for hard to reach biosensors such as a deep-water biosensors within a sediment microbial fuel cell. Furthermore, MFSc could play a major role in bioremediation, which is removal of organic pollutants from environments to produce clean water and excess electrical energy.<br><br>
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<h5>What is Microbial Fuel Cell?</h5>
 
<h5>What is Microbial Fuel Cell?</h5>
 
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Microbial fuel cells (MFCs) hold great promise for the simultaneous treatment of wastewater and electricity production. However, the performance of this system (Figure1) is currently poor, typically <10% of what is theoretically possible.
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MFC (Figure 1) is a device that utilises micro-organisms ability to catalyse an oxidation and reduction reaction at an anode and cathode electrode, respectively, and can produce electricity when connected to a load/resistor via an external circuit, whilst producing water at the cathode. <br><br>
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Recent investigation by a team at University of Westminster using dialysis sacks of well-defined molecular weight cut off (12000Da) studied mechanisms of electron transfer utilised by <i>Shewanella oneidensis</i> and reported direct mechanism contributed 63.6% to electricity production.
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Over expression of the proteins involved in direct mechanism namely: CymA, omCA, MtrA, MtrB and MtrC in S. <i>oneidensis</i> or in genetically tractable organism could enhance the performance of MFCs on electricity production and wastewater treatment.
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The aim of this project is to heterologously over express these proteins in <i>Escherichia</i> coli.
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MFC (Figure 1) is a device that utilises micro-organisms e.g. <i>Shewanella, Geobacter, Rhodoferax, yeasts etc.</i> to catalyse an oxidation and reduction reaction at an anode and cathode electrode respectively and can produce electricity when connected to a load/resistor via an external circuit and produces water at the cathode.
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<b>How microbial fuel cell (MFC) works</b><br><br>
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In anaerobic conditions, when no oxygen is present the microorganisms produce carbon dioxide, protons and electrons when consuming a carbon source. The architecture of a MFC capitalises on this principal to create electricity. Once the bacteria form a biofilm around the anode, and start to break down organic matter, electrons are striped from the carbon source by an oxidation reaction and translocated out of the cell via an electron transport pathways found only in these specific exoelectrogenic bacteria. These donated electrons are transferred to a carbon electrode (anode) and moved along a wire to a cathode. As electrons move through the wire, they pass through a resistor and an electrical current is generated. At the cathode the electrons reduce atmospheric oxygen to clean water with the addition of protons that are generated during the oxidation reaction. <br><br>
  
  
  
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<img src="https://static.igem.org/mediawiki/2015/e/e2/Team_Westminster_drawing.png" >
 
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<b> Figure 1</b>: Schematic of microbial fuel cells
 
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<h5>Statement of the Problem:</h5>
 
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Three possible mechanisms of electron transfer utilised by these microorganisms have been reported but ambiguously and poorly understood. The suggested mechanisms are: by direct electron transfer (DET) involving the use of membrane c-type cytochromes for transferring respiratory electrons to solid electrodes; mediated electron transfer involves the use of soluble redox-active molecules such as flavine mono-nucleotide (FMN) or phenazines to shuttle electrons from the electron transport chain to solid electrodes by diffusion. <br><br>
 
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In addition to the above mechanisms, electrons can also be transported to the electrode surfaces by using pilus-like appendages containing c-type cytochromes. These are termed as bacterial nanowires and are utilised by both <i>S. oneidensis </i>and <i>G. sulfurreducens </i>for distant transfer of electrons directly to electrode surfaces.<br><br>
 
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Using these mechanisms enable the microorganisms to build up multi-layered film, called biofilm on the electrode, which has been correlated with electricity production and products of metabolism like acetic acid, butyric acid and ethanol.  <br><br>
 
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Improvement of direct electron transfer mechanism in <i>S. oneidensis </i>or by heterologously expression of the proteins involved in a genetically tractable organism and application in MFC could enhance the performance of MFCs.
 
  
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<h5>Microbial Fuel Cell</h5>
 
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One major concern facing the modern world is the gradual depletion of fossil fuels and rising greenhouse gas emission. Microbial fuel is a device that holds a great promise for the sustainable production of renewable energy production in the form of electricity and bioremediation of organic waste from Industrial wastewater. It also offers potential to upgrade wastewater to useful chemicals e.g. hydrogen, bioplastics and biofuels<br><br>
 
  
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<video width="800px" height="auto" controls>
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  <source src=" https://static.igem.org/mediawiki/2015/f/f6/Team_Westminster_MFC_Video.mp4" type="video/mp4">
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<b> Figure 1</b>: Animated working model of a microbial fuel cell<br><br>
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Adapted from
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<a href=" https://www.youtube.com/watch?v=DVI6tMP-rOY/" target="_blank"> https://www.youtube.com/watch?v=DVI6tMP-rOY/</a><br><br>
 
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<h5>History of MFCs </h5>
 
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In 18th century, Luigi Galvani observed electric responses by connecting frog legs to metallic conductors. <br><br>
 
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In 1911, Michael C Porter provided evidence of electric production through microbial oxidation of organic compounds.<br><br>
 
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In 1960’s, National Aeronautics and Space Administration <b>(NASA)</b> proposed using human waste during spaceflight for electricity production. <br><br>
 
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In 1980, H Porter Bennett demonstrated using artificial mediators to enhance electric power production in MFC. <br><br>
 
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However, in past decade the discovery of extracellular electron transfer mechanism in microbes that allow them to survive in anaerobic environment that lack fermentable substrate e.g. glucose and conventional electron acceptors such as nitrate and oxygen but uses an insoluble solid surface as a terminal electron acceptor in order for them to breathe and survive, thus gave an important discovery in MFCs research. <br><br>
 
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Latest revision as of 00:14, 19 September 2015

Project Description

Shewanella oneidensis MR-1 is an important microorganism in bioremediation due to its diverse respiratory capabilities. It is a dissmilatory metal reducing bacterium. Being facultative organism, it has the ability to adapt to both aerobic and anaerobic environments, as well as utilise a number of toxic compounds such as manganese and uranium. It does this by accepting electrons, which gives Shewanella oneidensis the potential of producing electricity. An electron transfer pathway, known as the Mtr pathway, facilitates the extracellular translocation of electrons that are gained during the reduction of a carbon source.

The Mtr pathway consists of the following five genes:

  • OmcA - an outer membrane decahaeme cytochrome c
  • MtrC - an outer membrane decahaeme cytochrome c
  • MtrA - a periplasmic dechaeme cytochrome c
  • MtrB - a transmembrane porin which stabilises interaction between MtrA and C
  • CymA - an inner membrane tetrahaeme cytochrome c (Figure 1).

    • We have been working on introducing the Mtr pathway into Escherichia coli, in order to increase the electrical output in a microbial fuel cell (MFC). Shewanella oneidensis is capable of transferring these electrons through extensions known as nanowires. However, E.col have a far greater genetic tool set at their disposal, enabling easy genetic manipulation and modification. Further more, they are a very robust microorganism that, when compared to Shewanella oneidensis, are better equipped to deal with changes in a range of environmental variables, e.g. temperature and pH. The carbon source for our modified bacteria will be wastewater.

    We are exploring the possibility of electron transfer through the use of flagella found in E.coli K-12 derivative, DH5-α. E.coli should act as an anode. Formation of biofilm has also been noted in this strain of E.coli. The efficiency of the MFC is down to the biofilm, which is formed when cells adhere to a surface and stick to each other. The composition of these biofilms is what determines the amount of electricity produced as it acts like a conductive matrix, enabling higher kinetics rates of electron transfer along nanowires.

    This technology has a multitude of application. It could be used as an electrical source for hard to reach biosensors such as a deep-water biosensors within a sediment microbial fuel cell. Furthermore, MFSc could play a major role in bioremediation, which is removal of organic pollutants from environments to produce clean water and excess electrical energy.

    What is Microbial Fuel Cell?

    MFC (Figure 1) is a device that utilises micro-organisms ability to catalyse an oxidation and reduction reaction at an anode and cathode electrode, respectively, and can produce electricity when connected to a load/resistor via an external circuit, whilst producing water at the cathode.

    How microbial fuel cell (MFC) works

    In anaerobic conditions, when no oxygen is present the microorganisms produce carbon dioxide, protons and electrons when consuming a carbon source. The architecture of a MFC capitalises on this principal to create electricity. Once the bacteria form a biofilm around the anode, and start to break down organic matter, electrons are striped from the carbon source by an oxidation reaction and translocated out of the cell via an electron transport pathways found only in these specific exoelectrogenic bacteria. These donated electrons are transferred to a carbon electrode (anode) and moved along a wire to a cathode. As electrons move through the wire, they pass through a resistor and an electrical current is generated. At the cathode the electrons reduce atmospheric oxygen to clean water with the addition of protons that are generated during the oxidation reaction.


    Figure 1: Animated working model of a microbial fuel cell

    Adapted from https://www.youtube.com/watch?v=DVI6tMP-rOY/