Introduction to ecosystems
Introduction to ecosystems

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Introduction to ecosystems

4.1.2 Investigating flagellates

Dr Gianfranco Novarino is working on flagellates that occupy a very unusual ecosystem deep in the ground at Cape Cod, an organically contaminated aquifer – an underground water-bearing rock. It is, as he describes, a very basic ecosystem and probably one that you would not have thought of. Can you think why studying such ecosystems is important?

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Investigating flagellates

Gianfranco Novarino specialises in a group of flagellates involved in the cleanup of organic pollution.
A whale is made up of great many cells, a huge number of cells. And each cell is specialised in doing something very, very specific. Think about the poor amoeba or the poor flagellate. They are only made of one cell. And with that cell, they have to do everything that the whale does. So they are rather clever creatures.
In order to reach these flagellates, you have to drill down deep. The cores are collected from Cape Cod Air Force Base in America and sent to Gianfranco's laboratory in London.
The Cape Cod research started a few years ago. And it became immediately apparent that the dominant microbes inside the aquifer, apart from the bacteria, were flagellates, which occurred in only slightly lower numbers than the bacteria themselves. This was a fascinating ecosystem to study because it was very, very basic. We have bacteria breaking down organic substance and then we had the flagellates that were grazing on the bacteria.
A new technique called RNA probing allows Gianfranco to estimate the number of flagellates in the sample.
Conventional stains will stain DNA wherever it is contained. So it will stain every microbe in our preparation. On the other hand, by using the RNA probe, it is possible to stain only the organisms that we are really interested in.
The flagellates stain yellow. The bacteria don't show up at all. The next step is to prepare new samples to isolate and identify the organisms they contain.
The whole isolation process took a while. It was very exciting, even though it was a rather tedious job to isolate. And I think this really exemplifies very much of what research is all about. There's a lot of tedious, repetitive work, but if there is an underlying enthusiasm that motivates the researcher then that's really what research is all about. This is Tony, a totally undescribed flagellate from an organically contaminated aquifer that I've been studying for a number of years. It's about five micron in diameter, so pretty small. The reason why it has been named Tony is to honour Tony Manero, the star character of Saturday Night Fever in 1977. Tony Manero used to dance with one arm facing upwards and one facing downwards. And this is exactly how Tony swims. He can swim with one flagellum directed anteriorally and one directed posteriorally. Although, he can also use both flagella to project backwards. It's a beautiful organism. Obviously, this name will be changed to a proper scientific name, so a new name will be introduced in the literature. But it's very handy to have these off the cuff nicknames for new organisms that are awaiting formal description. What you can see here is another cell of Tony. It has slowed down in order to feed on these bacteria, in which you see a large number here in the background. And with a bit of luck we might just about be able to see the actual capture of a- ah, there it goes. Go back a bit. Watch this bacterium here. Now I can play that again. And it's gone. Nice catch for Tony.
When there's plenty of food, the boom times, Tony shows another behaviour that's typical of microbes.
Here you can see another cell of Tony. This cell has four flagella instead of two. The reason for that is that the flagella have replicated prior to cell division. What this cell will do eventually is divide into two daughter cells thanks to binary fission. In other words, when the bacterial populations in the aquifer are abundant there will be a population explosion of Tony. However, the story is very different when times are bad. When food is scarce cells of Tony produce a resistance stage, also called a cyst, which is a means to ensure long term population survival. The first thing that must be done is to settle down, come to a rest, and retract the flagella, as this cell is doing here. One flagellum has been retracted already. And the other one is in the course of being retracted. Eventually, this will produce a thick-walled resistance stage. We see a few cysts here, which is extremely resistant to heat, dessication, and of course, the absence of food.
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