Re: [DIYbio] Customize Microelectrode array

Like Nathan said, the Nature paper doesn't use any electrical signal from the bacteria. The bacteria made H2O2 and fluoresced. If your goal is to get an electrical signal, there are ways couple H2O2 levels to an electrical potential http://www.sciencedirect.com/science/article/pii/S0891584901006657 

On Thu, May 25, 2017 at 10:18 AM Abizar Lakdawalla <abizarl@gmail.com> wrote:

The voltage difference from inside a cell and the outside will be generated by ion pumps. Assuming that the difference in ions (Ca, Mg, Na, K, ...) will generate a differential charge inside the cell as compared to the outside. If you have a sense of which ions are responsible for the charge difference than the simplest way to detect this charge difference (= voltage) is by using intracellular dyes that measure Ca, Mg , ... or even more effective is to measure pH (H+ ions) with an intracellular dye. So put these bacteria under a fluorescence microscope and you will be able to see the voltage for every individual cell.

https://www.researchgate.net/publication/51328374_Intracellular_pH_in_Arbuscular_Mycorrhizal_Fungi_A_Symbiotic_Physiological_Marker

For detecting voltage changes in bulk you will have to make a microbial fuel cell (google it). 

On Thu, May 25, 2017 at 8:01 AM, Shambo Hore <shambo.hore88@gmail.com> wrote:

Dear Bryan,

I wish to do the voltage measuring experiment from IGEM 2008 project ( http://2008.igem.org/Team:Cambridge ) in https://www.nature.com/nature/journal/v481/n7379/full/nature10722.html module.

On Wed, May 24, 2017 at 1:08 AM, Bryan Jones <bryanjjones@gmail.com> wrote:

What are you trying to find? I don't know if you can measure potential with a setup like that. I'm pretty sure you'd need a complete circuit somewhere. A potential only exists between two points if electrons are being pumped between them. You can't have your reference electrode completely electrically isolated from your culture and get electrons pumped between them. I'm not sure how you could measure electrical potential in a suspension, but my coworker measures the potential generated by biofilms growing on an electrode. Her setup might help point you in the right direction. Here are the description and image of her reactor:

"While bioreactor design has varied greatly throughout the years and between labs, the design of the reactor for microbiological studies has recently converged. Figure1.8A shows a photograph of the most recent generation of electrode bioreactors.The conical chamber holds 15 mL of fluid, contains a stir bar, and is kept at aconstant 30 °C with a circulating water bath. All three electrodes (working, reference and counter) are placed in close proximity in the same chamber. Theworking electrode is a polished graphite flag with a surface area of 3 cm2. The graphite flag is attached to a loop of platinum with a Teflon screw. The counterelectrode is a piece of platinum wire. The reference electrode communicates with the solution across a Vycor frit. Calomel and Ag/AgCl are common referenceelectrodes. These electrodes are connected to a potentiostat. This system allows bacterial respiration to be continuously monitored in the form of electrical current. An example of current production by a wild type G. sulfurreducens biofilm is shown in Figure 1.8B. At any time during growth different electrochemical techniques can be performed on the biofilm, such as cyclic voltammetry (CV). This procedure scans current production at different electrical potentials. The rate at which the working electrode sweeps across different redox potentials can be varied. An example of a cyclic voltamogram is shown in Figure 1.8C."

On Mon, May 22, 2017 at 10:45 PM Shambo Hore <shambo.hore88@gmail.com> wrote:

Hi, I want to measure the potential changes in cell suspension caused by Bacteria with classical electronics system. Please advice me how i can setup the electronics system for this procedure.

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