Zombie Bacteria, Arrgg! Brains.
Posted on November 11, 2008
Filed Under By Mel
Before I left for Melbourne, I had set up an experiment to test how well the bacteria I was working on fixed nitrogen. This test ran for 7 days. After this point, I terminated the experiment and took some readings including cell numbers and iron oxidation. By looking at the cultures under the microscope, I determined that the bacteria were dead. I saw no movement or budding (bacterial division). Now because I was lazy I left the flasks containing the dead bacteria on my bench, instead of autoclaving and discarding them. I have had to give a few presentations and attend meetings since returning from Melbourne and as such, I haven’t been at my bench. Today I walked past the flasks and saw that the media had changed colour.
This was interesting because the bacteria should have been dead and therefore no iron oxidation possible, and no alteration of the media. There is always some abiotic oxidation (chemical processes) where ferrous converts to ferric without a biological catalyst (think rust on your car), but not to this extent. I re-examined the cultures under the microscope and to my shock they were alive. They are physically identical to the bacteria that I inoculated the flasks with, indicative of it not being a contaminant. So either they weren’t dead when I analysed them previously, which is entirely possible as they can hide on iron crystals, or something strange has happened. The conditions in which they were grown during the test were optimal in regards to temperature and movement, while on the bench there have been fluctuating temperatures and no agitation. In essence these conditions shouldn’t support growth.
I now have to set up this experiment again, and monitor any changes early on prior to cell death. Hiding zombie bacteria isn’t an explanation that I can publish.