Questions of bacteria

So what did my Year 9s decide to investigate with their new-found micro-biological skills?

In the end, the classes split about 50/50 into groups that had a very specific question – comparing the efficacy of different soaps, testing the 5 second rule, looking at the anti-bacterial properties of saliva (more on this later!) – and groups who just wanted to see what happened if they put stuff on the agar.

I wondered whether I should be frustrated by this lack of focus from the latter group, but in the end decided that they were simply displaying the genuinely curious approach of naieve scientists. They might not have formulated a hypothesis to test, but they were still exploring the natural world, poking it to see what happens, going “wow, that’s amazing!” when their plates disappeared under a luxuriant fungal foliage speckled with Staphylococci colonies…

But whatever shape their project took, the motivation and excitement of having complete ownership of their experiment was a joy to see. They could not wait to inspect their plates to see what had grown, to see what they had found out. Without exception, their write-ups reflected this, discussing their results thoughtfully and thoroughly.

So what did they find out?

Several discovered the importance of aseptic technique and the problems that can occur if you don’t employ it.

One very thorough and professional pair discovered that the fruit in the canteen did, indeed, accumulate more bacteria through the course of lunch time, as it was handled by more and more people.

I liked the project that sampled the locker handles from all the different year groups, suggesting that Year 7 are significantly less hygienic than any other.

There was a pretty graphic demonstration of the efficacy of Dettol – and several rather well planned projects that suggested the uselessness of washing hands at all.

Two groups showed very clearly that the 5 second rule has some validity – and I was amused by their comparison of apple, bread and jelly (!?!?). Splat.

And then there was dog saliva. A student managed to bring in a little vial of doggy drool from her canine pet. She and her friend set up plates seeded with E.coli and with paper discs soaked in the saliva. There were control discs, and comparison discs with human saliva and (wait for it) hamster saliva. Really? I asked, when they were preparing it. Yes, really. They were adamant they wanted salvia from the hamster.

So we awoke Herbie from his slumber and they persuaded him to chew on a cotton bud for a few minutes, and then rolled the cotton bud on the agar…

The hamster results were inconclusive, but there was no mistaking the huge halo of inhibition around the dog saliva. Awesome demonstration of lysozymic power!

Great fun, the whole thing, from beginning to end. And highly recommended.

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