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In the spirit of iGEM, our project’s aim is to design new biological systems that will make synthetic biology more accessible and friendly. Our team plans to achieve this by constructing a bio-electric interface, designing new selectable and counterselectable markers and characterising Citrobacter freundii to start a dialogue on what a synthetic-biology specific chassis should look like. For more detailed information on each of these sub-projects, refer to the links in the navigation menu on the left.
Project Abstract
As part of our project we will attempt to create a bioelectric interface - a way to connect biological and electronic systems in a standardised, inducible and quantifiable way.
To achieve our goal we will use the MtrCAB genes (cytochromes, proteins that mediate electron transport) from Shewanella oneidensis. We will transform E. coli with these genes along with a ccm gene cluster (cytochrome c maturation proteins) and couple it to an inducible promoter such as the Ars or Lac promoters which are induced by arsenate or lactose/IPTG.
As a result, we should be able to obtain a system that would allow us to measure the rate of electron export in response to an input of arsenate or IPTG. Possible methods to measure electron export include construction of a microbial fuel cell or the use of the ferrozine assay to measure the rate of reduction of iron (III) ions to iron (II).
We are also looking at two ways of making genetically modified bacteria safer to release into the environment:
Alternative Selectable and counter-selectable markers
Alternative to antibiotic resistance: We are investigating other ways to distinguish between the cells which have taken up the plasmid in question and those which have not in order to eliminate the need for antibiotic resistance selection. This would reduce the spreading of antibiotic resistance genes if an engineered bacterium were to be released into the environment either deliberately or by accident.
Chassis characterization: Citrobacter freundii
We intend to characterize this 'friendly lemon bacterium' (a member of the gamma-proteobacteria, like Escherichia coli) in order to assess whether it would be a good chassis for cloning and gene expression within synthetic bioloy and beyond. We want to see what it can offer to this field to assess whether there are some new things it can do, or can do better than E. coli , the legacy chassis.
We also aim to characterize various criteria which would have to be known in order for researchers to start using it as a novel chassis. In addition to characterizing its growth requirements and BioBrick compatibility, we hope to sequence its genome to gain more insight into its metabolic pathways and novel genes.
Finally, we want to assess whether public opinion would favour the less known but safer Citrobacter freundii over Escherichia coli, which may have a bad reputation due to its association with disease, sewage and ability to become pathogenic if exposed to wild type strains.
