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Team:Lethbridge/Project
From 2009.igem.org
Contents |
Overview
The project will focus on the cyanobacterium, Spirulina maxima, a photosynthetic blue-green algae, which has been shown to produce an electrical current. S. maxima has been shown to generate up to 800 mV of electricity per cm2, and although this does essentially provide enough energy to charge a battery, it may simply not be enough to sustain the battery once it is being used. Therefore, we must optimize its electrical output and create the BioBattery.
Further to the development of the BioBattery itself is the generation of applications for the batteries use. One such application would be to generate the voltage necessary to electroplate a material. A significant challenge to this project is that the majority of metals are toxic to cellular functions. Sulphate-reducing bacteria, however, can cause certain metals, such as zinc and copper to aggregate into nanoparticles which will precipitate out of solution. Recently, these bacteria have been found to excrete certain proteins which can cause these particles to aggregate in large spheroids, up to 100 nm in diameter. The proteins from these bacteria could potentially be used to reduce and aggregate the metal ions together into nanoparticles which will then precipitate out of solution, maintaining bacterial levels and subsequently allowing the metals to deposit onto a surface. Generation of a voltage across the material from our BioBattery, could induce the metal particles to distribute evenly, effectively plating the material with metal. This sort of BioPlating would offer an inexpensive alternative to a very expensive procedure when performed classically.
We will be utilizing the microcompartment found and characterized from Aquitex aeolicus and optimizing it for the targeting of desired materials into the compartment. The generation of such a microcompartment would act to revolutionize the synthetic biology approach, allowing for easier cloning strategies, bringing enzymes from various organisms which might not normally work in conjunction into close proximity, minimizing side reactions and allowing for the formation of efficient novel metabolic pathways. There are sub-projects which will be completed on the way to the final goal of the production of the BioBattery which are outlined as:
1)The compartmentalization of cellular photosystems:
The lumazine synthase protein of many bacteria (ribH gene) has been shown to produce 60 subunit icosahedral capsids. Towards this end, Seebeck and colleagues were able to engineer an electronegative surface in the pore of the assembled capsid [Seebeck et al. (2006) J. Am. Eng. Soc.]. By attaching a positively charged tail onto the terminus of green fluorescent protein, the protein was targeted into the capsid, and its fluorescence was observed. We will attach arginine tags (10X Arg tags) to the termini of proteins to be targeted, as well as a synthesized biobrick encompassing the ribH gene. We intend to demonstrate co-localization of two fluorescent proteins (cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP)) to the interior of the capsid using bioluminescent resonance energy transfer (BRET). This will be used as a proof of principle system prior to organization of the cell’s photosystem into this compartment.
2)Novel electron facilitators
Upon successful targeting, it is feasible that the incorporation of a novel electron shuttling protein into the engineered microcompartment would increase the current generated by facilitating electron movement to the electrodes of the microbial fuel cell. Indeed, many MFCs use mediators to increase their efficiency; however, these substances tend to be expensive. Towards this end, we have identified the gene encoding for naphthalene dioxygenase, ndoB. This protein is involved in the formation of humic acid, a common electron mediator, in soil bacteria such as Pseudomonas aeruginosa.
3)Production of nanoparticles
Many applications which require the use of nanoparticles, such as medical and diagnostic sciences, require that the particles adopt uniform structures and sizes. Current methods used to produce these nanoparticles are cost intensive and require extreme conditions and harsh organic solvents [Amemiya et al. (2007) Biomaterials]. However, bacterial strains have been found that produce these nanoparticles with specific sizes and distinct morphologies. The proteins involved in the process the nanoparticle production are being characterized to create a better understanding of the process. A protein of particular interest to us is mms6, produced by Magnetopirillum magneticum, has been found to be key in controlling the morphology of the particles. This protein shall be introduced into E. coli with the intention introducing a novel method for the mass production uniform nanoparticles which is efficient and cost effective.
