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Ellen McCallie's Carriacou diary: Bugs and barometers

Updated Monday, 28th January 2008

Keeping the germs at bay – the Rough Science team set about making an antibacterial cream.

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Day 1

This is a tough challenge; it’s very interesting, too, but I’m a bit worried about a couple of things.

First, Mike L and I don’t get on too well, but we both like good challenges. In the next three days, we are really going to have to focus on the work at hand, putting aside everything else. I guess this is why science is such a good cross-over sport - what I mean is people from different cultures, different religions, different languages, different perspectives can often work together if they share a common goal. Science and/or figuring out things often carries a common goal with it. I’m just going to take a deep breath, get over it and do good work. I expect that Mike L will do the same. Heck, making a microbiology lab out here will be quite a trip.

In college I laughed when we were handed agar plates. I always wanted to eat them because in high school, when I was an exchange student to Bogor, Indonesia, we would eat agar with coconut milk and other flavorings. I loved it. The texture was amazing. It was soft, but firm, I could separate the flavored layers with my tongue. It is like playing with Wisconsin string cheese!

It took me seven months to finally understand what agar was - a seaweed algae that has been cooked down. The polymer chains (carbon chains) in agar change their structure depending on their environment. Basically, when the seaweed is in calm or deep water, the polymer structure of agar is a soft gel, allowing nutrients to be absorbed into the seaweed. When the tide goes out and the seaweed is exposed (and bashed by waves hitting them and rocks), the polymer structures in agar change; they add sulfate groups which cause cross-linking. In any case, the gel becomes firmer and protective.

Our goal is to induce the hard gel properties, so we have a firm medium on which bacteria can grow. The food industry often uses agar in the soft gel form to make foods smooth and creamy.

It isn’t any seaweed that forms agar, however. It is a red seaweed, that often looks brown - just my luck - and looks like it has two-fingered hands at its tips. This is nuts. I’ll just have to go diving to see if I can find some.

Dr. Fran Hanzawa, a professor of mine while I was at Grinnell College, once told me her Major Professor told her to go find seedlings of Trillium grandiflorum. He didn’t know what they looked like, but she should go find some. This is how I feel, even though I have a clue as to what the seaweed looks like - I have a whole ocean to search.

Day 2

I found the right seaweed (Chondrus crispus). I’ve boiled it up (and boiled it and boiled it). I never realized how much biology and chemistry depend on heat. Heat causes reactions and speeds up reactions. We’ve got gel to add bacteria to. The meat broth I made is to give the bacteria nutrients so they can multiply.

Day 3

Why try garlic? Surely, you must have seen the ads that claim garlic will cure you of anything and everything. They have been advertized for at least two hundred years. Plus we know garlic is safe for human consumption, even in high quantities - my college friends are a case in point. We even ate garlic ice cream thanks to a buddy of mine, Rob White. So is garlic the miracle cure? Let’s start by seeing what it does to bacteria.

The oil from wild sage is known locally as a bacteriacide - "kills germs". Why not test it!

So why yucca? (It is actually agave (Agave caribeaicola), but once you goof and say it wrong all day on television, you have to stick with your mistake. It is too hard to correct. This is reality TV after all.)

Agave, looks like a big aloe plant and it is also fairly closely related to aloe. Aloe is known to promote healing. That doesn’t mean it kills bacteria, but I was curious to see what it would do. These are long lived plants that seem to have few infections and blemishes on them.

We made three replicates. In other words, in order to have confidence in our results we tried everything three times, just in case one (or more) of our tries ended up strange. For example, what happens if I thought I dipped the pipette in the wild sage, but I actually dipped it in the yucca by accident and didn’t know it? The results for that plate would be inaccurate, but I wouldn’t know it. The liklihood of me doing the wrong thing three times is much less than if I only did one try of each thing. 'Minimizing the likelihood of errors' or 'improving accuracy' - that’s why we make replicates ('repeats').

Why did we use a control? What is a control anyway? I think of a control as what would happen if you didn’t do anything. In other words, we grew bacteria on agar plates with beef broth for bacteria food. If we didn’t put a bacteria-killer on the plates, what would we expect? (Tons of bacteria to grow.) A set of control plates with lots of bacteria lets us know that everything is going as it should. If the control plates didn’t have bacteria, then we’d know something was wrong with the agar, our sampling of bacteria from Mike B’s mouth, or something else. The important thing is that we wouldn’t make the mistake of saying all the treatments, garlic, wild sage oil, and agave, are great at killing bacteria. We’d know there wasn’t bacteria there in the first place.

Okay, so we have control plates to make sure everything is as expected and also to see what happens if you don’t add a treatment.

As it turns out, our results were pretty consistent among plates of each treatment (each thing we tried). The garlic was the best in all three of its plates, then the wild sage oil, then the agave, and then the control plates which were covered in bacteria.

Hey, this challenge worked out okay! And wasn’t Kathy’s microscope the coolest thing ever!





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