We had to do a practical measuring the effectiveness of four different agents against Bacillus Subtillus - a bacteria. The four agents we used were water, bleach, antiseptic and Penicillin.  We were carrying out this practical using aseptic techniques. We had to make sure there was no possible way of our Petri dish or anything else we were using being contaminated with something from the air or from somewhere else.  This part of the process made the practical even more interesting, as we had to think really carefully about how to calculate the 'clear' area of the cross-section.

The results were surprising.  The Penicillin had the least amount of clearance which either could mean either Penicillin itself doesn't work against Bacillus Subtillus or maybe that particular batch was out of date or it could have just been an anomaly. In order to verify this, we would have to repeat the practical a few times and cross-reference the results to find out why the penicillin didn't work.  The agent that had the highest amount of clearance was the antiseptic, then bleach, and then water.

Overall, this was a really fun and interesting practical that made us really think.  Our thanks to all the lab technicians that prepared all our equipment beforehand and look after everything for us!

Ananya Kikeri, Year 9