Question: What is the most interesting effect one of your chemicals has had on bacteria?

Robert Hampson answered on 7 Nov 2014:

Its quite hard to describe in an interesting way because its not like the bacteria jump out of the dish and start doing a song and dance. However, I will try to explain why it is interesting…

The bacteria in question (Staphylococcus aureus) releases a molecule called AIP. It also has a sensor which measures the amount of AIP in the area. Because each bacteria is releasing AIP, lots of AIP means lots of bacteria. When there are lots of bacteria, the AIP sensor is turned on and the bacteria attacks the human host to make more room and to get more food. Unfortunately this isn’t very good for the human host. One of the molecules released by the bacteria is called haemolysin. Haemolysin pops red blood cells so the bacteria can grab the iron which is contained within. However, you need your red blood cells to provide oxygen to your body and the stress of having lots of popped cells floating around your blood also makes you feel ill.

My molecules specifically stop the AIP sensor turning on. This prevents the bacteria knowing that there are lots of other bacteria around. This, in turn, means it then doesn’t attack the human host and doesn’t release all of the nasty proteins including haemolysin.

There is a cool experiment I sometimes do with rabbits blood which shows the effects of haemolysin. First I grow the bacteria overnight at 37 degrees in a liquid called BHI (Brain and Heart Infusion which is made from ground up brain and heart from Cows). Then I spin the bottle really fast in a centrifuge so all the bacteria stick to the bottom of the bottle. I take some of the liquid and add it to rabbits blood and wait 15 mins. I then spin the rabbits blood really fast so all the cells stick to the bottom of the vessel.

With normal bacteria, the liquid is red because the bacteria released loads of nasty haemolysin and many of the red blood cells in the rabbit blood have popped releasing their red insides. However, if I add my chemicals to the bacteria when I grow them overnight, the liquid remains colourless like water. This is because my molecules have blocked the AIP sensor and consequently the bacteria have released no haemolysin and they therefore can not pop the red blood cells.

If I can stop bacteria being harmful to humans like this then it may be possible to invent new antibiotics that don’t actually kill the bacteria but just stop them from harming humans. I think that is pretty interesting!