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Natural Selections: "A Field Guide to Bacteria"

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Martha Foley and Dr. Curt Stager discuss Betsey Dexter Dyer's book, A Field Guide to Bacteria, and the distinctive traits of individual bacteria that are visible to the naked eye.

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Martha: Okay, you’ve introduced me to yet another field guide. Kind of a surprising one, I do have to admit although I’m interested in all sorts of things. A Field Guide to Bacteria.

Curt: It doesn’t come with a microscope

Martha: Now aren’t they a little small for a field guide?

Curt: Yeah but it’s sort of an attention-grabbing title. But in fact, there is such a book. It’s from Comstock Publishing and the author is Betsey Dyer. But her point is that, yeah the individual bacteria are tiny, but they occur in such huge numbers and often have colors or emissions that are noticeable to the naked eye that you can actually go around looking at habitats and identifying the kinds of bacteria by what you see with the naked eye.

Martha: Is it full of beautiful photographs like other field guides now are?

Curt: It depends what you mean by beautiful. But photographs, yeah, bubbling, let’s say.

Martha: Well, tell me some fun facts from the field guide.

Curt: The introduction's really neat actually, because she’s really into microbial life, which most of us are not that aware of. But she makes some really interesting points and says that we think that a bacterium is small, but we’re the weird ones. That if you add it up what most of life is, it is these microbes, and we’re strange because we’re so big and multicellular. It’s a fun introduction, but then she goes chapter by chapter with basic types. And one of these types of bacteria--they’re called alphaproteobacteria--but it turns out that you can actually see evidence of them existing with the naked eye.

Martha: Now some bacteria make scummy things, I mean you can tell when bacteria are there. Is that what you mean? Kind of like there’s so many of them or they’re doing such weird things?

Curt: Yeah, things that you wouldn’t even really connect with a living thing. Like if you walk to a wetland. I see this all the time; you walk by some of the boggier marshy areas and you see this kind of rusty cruddy looking sediment or color to the water.

Martha: Like a film on top you mean?

Curt: Yeah, and sometimes there’s this sort of a shiny metallic film on top but that’s not just chemicals, that’s produced by these bacteria as a sort of a waste product, they precipitate out metals like iron, or in the case of that shiny scum, its manganese.

Martha: Well if you touch that it breaks. I mean it actually breaks.

Curt: Yeah it’s a little thin sheet of metals. And that will shatter like little ice flows. The rust too, like if you find an old pipe lying in a place like that that’s crusted with rust and full of it. Some of that is normal rusting, but a lot of that is precipitated by the bacteria. Same as if you ever watch on TV, or if you’re lucky enough to go to a big old ship wreck under the se,a and it’s so clumpy with the rust and stalactites and icicles of rust--that would actually be the bacteria stuff. So with the naked eye you can see it. Another neat thing about these metal-loving bacteria is that a lot of them make natural magnets inside of their cells out of the iron particles.

Martha: It’s like a compass? They don’t get lost?

Curt: They don’t get lost in the woods. And it’s funny, if you look at them under a microscope, they actually get these little tiny crystals of magnetite--basically iron ore--and they make a line out of them, a row, and they wrap it up in a membrane, and it’s actually a magnet.

Martha: What do they use it for?

Curt: It helps them orient with the Earth’s magnetic field to tell north and south. Why do they care? No one really knows. One speculation is it actually--ironically--tells which way up and down is, which can be important if you’re in this wetland or in sediment or a soil. If you go up and down you’ll get more or less nutrition or oxygen or whatever you need. These things don’t have a brain or eyes or anything.

Martha: Say are these related to bog iron? You know, Vikings, I could never figure that out--they would find iron in the bog.

Curt: Yeah, Vikings used to do this in Europe and actually lots of other cultures in certain kinds of bogs. If you dig down in there are these crusty chunky layers of rust, which again is from these kinds of bacteri, and they precipitate out--sort of molecule by molecule--this iron. Europeans had figured out--and other cultures too--how to take that and heat it to about 1,000 degrees and get the iron out of it. Again it’s from bacteria. You never would have thought it.

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