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Team:Cornell/testing/project/wetlab/4/7
From 2012.igem.org
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Wet Lab
- Overview
- Chassis
- DNA Assembly
- Testing & Results
- Future Work
- Animation
Reactor Testing
Overview of Characterization in Bioelectrochemical Stystems
As described in the Chassis section, S. oneidensis MR-1 is capable of shuttling electrons through the Mtr pathway to reduce Fe(III) to Fe(II) because of the negative free energy change associated with the redox reaction. Thus, to encourage Shewanella to transfer electrons to an electrode, we poise the redox potential of an electrode to that of Fe(III)/Fe(II) in a three electrode system, controlled by a potentiostat. [[LINK TO THE PAGE ON THE POTENTIOSTAT]]. In short, this instrument works by setting the potential of a working electrode (WE) with respect to a Ag/AgCl reference eletrode (RE) by injecting current through a counter electrode (CE). These electrodes can be seen in the schematic representation of our single-compartment bioelectrochemical reactors shown below.
First Lessons Learned: Control Reactors
In order to enhance the field-deployability of our final device, we initially decided to feed our reactors with LB, since a very concentrated LB source fed at a low flow rate could sustain our field reactors for extended periods of time without taking up much physical space. However, upon setting up control reactors—both in batch and continuous flow operation—we discovered that wild type S. oneidensis MR-1 produced significantly less current when fed with LB than M4—a commonly used media for Shewanella-inoculated bioelectrochemical systems.Naphthalene & Salicylate Sensing
First characterized naphthalene sensors with salicylate, since our system indirectly senses naphthalene via salicylate.Uninduced salicylate reporter produces same current as MR-1 in rich M4 media.
First attempt to diagnose problem: Switch to minimal M4... Producing higher current, but we're still not getting a salicylate response.
Next attempt: Poise the working electrode at a higher potential in attempt to get more MtrC and MtrA for MtrB to associate with. Didn't quite do the trick either.
