Post on 19-Aug-2014
description
iGEM 2014: UC-Santa Cruz-BioE
Sai Edara - Biomolecular EngAaron Maloney - Bioelectronics EngMarshall Porter - Biomolecular Eng
David Dillon - Biomolecular EngChristian Pettet - Biomolecular Eng
Arjun Sandhu - Biomolecular EngAnsley Tanoto
Alex Ng
● Undergraduate Synthetic Biology Competition put on by MIT.
What is iGEM?
● Undergraduate Synthetic Biology Competition put on by MIT.● Students from universities around the world work with a kit of biological
parts, and parts they design, to build biological systems
What is iGEM?
● Undergraduate Synthetic Biology Competition put on by MIT.● Students from universities around the world work with a kit of biological
parts, and parts they design, to build biological systems
What is iGEM?
● UCSC’s debut year at the jamboree held in Boston, MA will be "...the largest single event in the history of the iGEM (International Genetically Engineered Machines) competition and synthetic biology "
● This year we are working with the bacteria Shewanella oneidensis to increase efficiency of a microbial fuel cell, a technology capable of turning waste water treatment into a power generating process.
iGEM at UC Santa Cruz
Waste-water treatment ● Treatment of waste water can be divided into three main steps
1. Heavy and light materials are removed by separation in a holding tank2. Microorganisms are used to break down organic matter3. Water is disinfected to be reintroduced to environment
http://en.wikipedia.org/wiki/Sewage_treatment
The bacteria Shewanella oneidensis
● Can live in both environments with or without oxygen
● Can reduce poisonous heavy metal
● Has “electrogenic” properties allowing it to generate electricity in a Microbial Fuel Cell (MFC).
http://www.newscientist.com/article/dn9526-bacteria-made-to-sprout-conducting-nanowires.html#.U9gp_LEzCM0
What is an MFC?● Microbes Break down
Carbohydrates● Transfers electrons to anode,
which then flow to the cathode● Protons pass through
permeable membrane● Protons and electrons react
with oxygen to make clean water
● Can be implemented into secondary treatment of waste-water to allow for power generation[5] http://www.sciencebuddies.
org/Files/3665/5/Energy_img033.jpg
Physical Design● A lot of previous research has
looked at structural design● Two main points
○ Large surface area on electrode
○ Close distance between electrodes
● 3D Model for casing Designed by iGEM 2013 Team Bielefeld (Germany).
● Files converted into 3D printer files and printed. http://2013.igem.org/Team:Bielefeld-
Germany/Project/MFC
Our Project● We believe the bacteria which drive the power generation of an
MFC can be genetically engineered to create more power● Design MFC with increased efficiency by
○ Altering metabolism of our electrogenic bacteria○ Modifying growth pattern of biofilm formation
● Two pronged approach, each with potential to improve efficiency alone
Energy Balance and Coulombic Efficiency
● The process of metabolism and electron transfer is complex.
● The cell itself uses up some of the energy in other processes
● One such process is metabolite generation, which reduces coulombic efficiency.[1]
● We plan to redirect metabolism toward a pathway capable of harvesting the lost energy
● When Shewanella is grown without oxygen, it generates the metabolite acetate from acetyl-coa
Acetate generation
[3]
● “gate keeper” to the TCA cycle● Converts acetyl-CoA and
Oxaloacetate to Citrate● Diverts Acetyl-CoA from being
converted to Acetate (metabolite)
Citrate Synthase (GltA)
● Under anaerobic conditions Shewanella is capable of using the oxidative branch of TCA, which will produce more energy lost by metabolite generation
● Use of oxidative branch is reliant on Citrate Synthase activity
Oxidative branch
Oxidative branch of TCA
Citrate Synthase● Under the anaerobic conditions citrate synthase activity
reduced by over one half due to downregulation of the gltA gene coding for citrate synthase [3]
● In our project we will recover this activity using an expression plasmid
(gene deletion)[3]
● Magnitude of electron transfer reliant on surface area of the anode○ More surface area allows more bacteria
to transfer electrons○ Growth of bacteria in biofilm allows for a
dense community to grown in one area● Growth of Shewanella in anaerobic
conditions leads of down regulation of biofilm production, and biofilm density is lost
Biofilm
Steps in Biofilm growth: 1 2 3 4 5
http://en.wikipedia.org/wiki/Biofilm
Biofilm● Biofilm formation in Shewanella is
controlled by the gene mxdA, which regulates levels of c-di-GMP
● Upon deletion of mxdA, biofilm biomass decreases (fig A, mxdA)
● Biomass also decreases when switching from oxic to anoxic growth (fig B, control) but is retained when a gene similar to mxdA is expressed (fig B, VCA0956)[7]
● We hope to express mxdA in anoxic conditions [3] to increase biofilm density
A
B
[7]
Citations1. Korneel Rabaey, ed. Bioelectrochemical systems: from extracellular electron transfer to biotechnological application. IWA
publishing, 2010.2. Franks, Ashley E., and Kelly P. Nevin. "Microbial fuel cells, a current review." Energies 3.5 (2010): 899-919.3. Brutinel ED, Gralnick JA. Anomalies of the anaerobic tricarboxylic acid cycle in Shewanella oneidensis revealed by Tn-seq.
Mol Microbiol. 2012 Oct;86(2):273-83. doi: 10.1111/j.1365-2958.2012.08196.x. Epub 2012 Aug 27. PubMed PMID: 22925268.
4. Papagianni M. Recent advances in engineering the central carbon metabolism of industrially important bacteria. Microb Cell Fact. 2012 Apr 30;11:50. doi: 10.1186/1475-2859-11-50. Review. PubMed PMID: 22545791; PubMed Central PMCID: PMC3461431
5. Rabaey K, Verstraete W. Microbial fuel cells: novel biotechnology for energy generation. Trends Biotechnol. 2005 Jun;23(6):291-8. Review. PubMed PMID: 15922081.
6. Beliaev, Alex S., et al. "Gene and protein expression profiles of Shewanella oneidensis during anaerobic growth with different electron acceptors." Omics: a journal of integrative biology 6.1 (2002): 39-60.
7. Thormann, Kai M., et al. "Control of formation and cellular detachment from Shewanella oneidensis MR-1 biofilms by cyclic di-GMP." Journal of Bacteriology 188.7 (2006): 2681-2691.