January Update: Bio-sciences Group

Since the engineering group has given us the prototype we have been working hard to test the capacity of it! Quantifying bacterial growth is hard work, but we found a system that will give us a pretty accurate number of bacterial colonies killed.

First we grow a simple strain of lab grown E. coli. Using a previously tested estimate, we are sure when saying there are about 10^8 or 10^9  CFU/mL or 100 million colony forming units per 1 milliliter of broth. In plain English, a lot of bacteria in a test tube.

This is the plate we made after swabbing a bin we got from the security line at the Oklahoma Capitol building.

In order to properly plate this broth, we need this number to go down by about 10-7 so we need to dilute the broth. We used a process called serial dilution.

Each vile only has 1 mL of liquid in it, so it is much easier to dilute the bacteria is a small series of dilution rather than one very big dilution.

Once we have a countable amount of CFUs (ideally 10^2) we are ready to put on a petri dish and run through the sanitizer. Our positive control for the plate will allow us to know how many colonies should have grown if the experimental plate had not been run through the sanitizer.

On the right is the positive control, this is not get exposed to the UV light in our machine and therefore grew E. coli colonies. On the left is the experimental plate, this was exposed to the UV rays in the machine for 4 seconds and did not grow any colonies!

We are planning on running many more trails so we have accurate data but right now we estimate the Auto-Sanitizer kills off around 95% of bacterial CFUs!