TRANSCRIPT
Girl1: Hi. Are you Mr. Greg Frank?
Man1: Yes. You must be the tree house detectives. I hear you have some Petri dishes for me to look at.
Girl1: This is the one form the tree house. This is the control dish.
Man1: It looks like you've been very careful in labeling these dishes.
Girl2: We made sure that each dish was only open for ten minutes at the same time of day so that any microbes would have the same chance of growing.
Girl1: And to make sure we were manipulating only one variable, we've kept them together for the last twenty-four hours.
Girl2: So that they have the same growing conditions.
Man1: Let's take a look at them under this dark field colony counter. It will illuminate the colonies and make them larger.
Girl1: Wow. This is pretty cool. I count forty-five colonies in the tree house dish. I couldn't see anything yesterday. What's happened.
Man1: Individual bacterial cells are so small they're hard to see with your eye and even some microscopes. However they grow so rapidly that over a twenty-four hour period they grow from one to over a thousand cells and that's what you're seeing in these colonies.
Girl2: There are about fifteen colonies in my dish.
Girl1: The control dish doesn't have any colonies.
Man1: Why do you think the tree house has more colonies?
Girl2: I think it has something to do with the fact that the tree house is outside.
Man1: That could be one reason.
Girl1: Doctor D warned us that it's hard to control everything.
Man1: Perhaps the tree house is not as isolated as you thought.
Girl1: We know that microbes like bacteria and viruses cause diseases, but we don't know much about them. Can you tell us about microbes?
Man1: It would be very difficult to show you viruses since they are so small, but let's take a look at some bacteria. We can remove them from the inside of your mouth with this swab.
Girl2: RJ told us that there are bacteria in us all the time. Even when we're not sick.
Man1: Let's rub this sample on a clean microscope slide. Before we look at it, let's stain the cells so we can see them better.
Man1: Let's magnify this a thousand times and project it onto the TV monitor.
Girl2: There are lots of different shapes. What's the round one?
Man1: That's bacteria that we call a coccus.
Girl1: That one looks like a cylinder. What's it called?
Man1: We call that a rod shape or a bacillus bacteria.
Girl1: That bacteria's round, but it's in chains.
Men1: Yes. We call that one a streptococcus.
Girl1: Is that like strep throat? Does that mean I'm sick?
Man1: Not necessarily. There are other bacteria that look like the strep throat kind, but they are actually beneficial to us.
Girl2: Are you saying that bacteria can be helpful?
Man1: Most bacteria are good. And in fact, we couldn't survive without them.
Girl2: I never thought about bacteria being good.
Man1: Think about termites. As you know, termites eat wood, but they cannot digest it. It is the bacteria in their gut that digests the wood. This is also true of our own stomachs where a bacteria know as E. coli helps us digest our own food and produce vitamins.
Girl1: What about the bad bacteria?
Man1: Some bacteria enter our cells and destroy them from within. Others produce very deadly toxins like botulism.
Girl1: If bacteria can multiply so fast and cause so much damage to the body, how do we survive?
Man1: The body has its own defense system to fight off disease. It's called the immune system. And most of the time it keeps us pretty healthy.
Girl2: It sounds like we need to learn more about the immune system.
Girl1: Thanks Mister Frank.
Man1: You're welcome. Good luck and come back if you need anything else.