Science Forums 2

[Michaelangelica]

Thanks CE
this is the transcript from an ABC radio show. Not really on soil bugs but. .
You can listen to the show for the next few weeks or just read the transcript

Anyway Giselle, what's your ambit; what beasties do you include in your swag of little things?

Giselle Walker: There are creatures which don't have cells,

• which are viruses
• and there are reproducing molecules that don't have cells, which are prions, but they're fairly easy to distinguish from things that
• are cellular which include bacteria, eukaryotes and archaea.

So archaea basically look like bacteria but they live in weird places and they run on weird chemistry.
Bacteria are the things that everyone's familiar with, things like E. coli and staph aureus.
Eukaryotes we're all familiar with but people probably don't realise what they are; they're cells that have their DNA stuffed inside a nucleus.

Robyn Williams: That's us, isn't it?

Giselle Walker: That's us, that's plants, algae, protozoa and slime moulds and about 95% of the eukaryotes are single celled which points out that animals in general are a tiny, tiny blip of diversity both in terms of abundance and in terms of cellular diversity or genetic diversity.
And so what I work on is basically the rest of the eukaryotes, minus the plants and minus the fungi because there again, they're a bit big for me to look at.
. . .
. . .
Robyn Williams: It's interesting. Now when it comes to becoming multicellular, I'm always fascinated by that creature called the slime mould, in fact Dictyostelium is one of my favourites, which goes around as a bunch of unicells in the earth and then somehow a signal comes and they all get together and they form a slug-like object with a back and a front end, almost like a snail and go off and reproduce. I mean is that the kind of beginning of multicellularism where it's optional or is that a weird off shoot?

Giselle Walker: Interestingly that has happened in a whole bunch of different groups. You can divide the eukaryotes up into six major groups.

• One group includes the animals and fungi;
• another group includes amoebae and things like Dictyostelium.
• Another group includes plants and red algae;
• another group includes weird stuff like Giardia

and in this group that contains weird stuff like Giardia is the organism that I work on, which also does slime mould morphology. It's called Acrasis rosea and so it crawls around as a set of amoebae in the earth most of the time and then occasionally when you have a particular pattern of dark-light cycles it decides to make a little tree and some spores and disperse. And you can induce this in the lab
. . .
In terms of us versus these squillion other things living in our guts, yes, there are a lot.
I tend to work on the things that live in termite guts rather than in our guts, so I'm looking at convergent evolution in termite flagellates which are the things that termites use to digest their cellulose.
So these little unicells that live inside the guts of termites seem to have relatively similar morphologies no matter which set of termites they live in or indeed if they live in a cockroach.
And this appears to be something to do with the physical constraints of living inside a cockroach or a termite rather than actually being to do with the relationships between these different organisms
. . .
. . .
So something I'm doing at the moment is looking at convergence of these different hydrogenosomes and trying to characterise the organelles in one particular type in an organism called Breviata anathema, which I studied during my PhD.

Robyn Williams: Anathema.

Giselle Walker: Anathema. There is a time honoured tradition in taxonomy of trying to get silly names into the literature. I'm definitely not the best exponent of it but the lab I was in in Sydney was known for this and so anathema was my best effort so far. There have been many other taxa like fornicata and Massisteria marina and Euglena viagra, which is also quite a good one.

Robyn Williams: Mike Archer got I think Montypythonoides turned down at one stage for some weird fossil.