Leptothrix discophora? Leptothrix discophora is a
bacterium that uses iron the way we use oxygen. Some people describe
this process as "breathing iron." L.
discophora embeds itself in an iridescent film of its own making. The film is visible to the naked
eye and often looks like an oil slick. Here is a
photograph of an L.
discophora film. Hit your
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link to return to
What are iron bacteria?
Iron bacteria are bacteria that use iron to maintain their life
functions. A few
iron bacteria are Leptothrix
ochracea, Gallionella ferruginea, and Toxothrix trichogenes. L. discophora's iridescent
filmcan be detected by the
naked eye. The bacterium itself is too small to be seen except under a
microscope. Other species of iron bacteria, also too small to be seen
by the naked eye, can be detected by their products, called
"flocculates," or "flocs" for short. Flocs have a variety of textures,
depending on the bacteria producing them, but most have the color of
rusted iron and are, in fact, iron oxide. Here is a
photograph of an iron floc. Hit your
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link to return to
Do bacteria live
on other metals
Yes, some bacteria metabolize (eat) or respire (breath) manganese,
sulfur, copper, silver, zinc, nickel, uranium, or gold. Some of these
bacteria make use of more than one chemical element. How
Worldwide, scientists have identified thousands of mineral-utilizing
bacteria. How many
different kinds of iron bacteria live in Ohio's Vermilion
Perhaps only about 50 kinds of iron bacteria live in the Vermilion
River and on the minerals in the river rocks. Are these microbes
Bacteria that live on minerals are only a problem when their growth
runs rampant. Such rampant bacterial growth occurs at poorly maintained
or abandoned coal-mine sites, where the problem is
called acid-mine drainage. In the relatively clean Vermilion River the
growth never reaches this level, and the bacteria can be enjoyed for
their often beautiful appearance. How can you tell
the difference between an oil slick and a film of Leptothrix discophora?
Run your finger or a stick through the film. If the film flows back
together, it is oil. If it shatters, it
is Leptothrix discophora. What accounts for
the colors in a Leptothrix
Many factors contribute to the appearance of a Leptothrix discophora film, but
perhaps primary is the optical phenomenon known as thin-film
interference. Interference colors occur, in this case, when white
light—composed of all the wave lengths in the rainbow—hits the L. discophora film and bounces off
the top and bottom of the film. When the light bounces back up from
both surfaces, the rays are out of sync, and the various wave lengths
interfere with each other, reinforcing some colors and suppressing
others. What colors become visible is determined partly by the
thickness of the film. You can also observe thin-film interference in
soap bubbles and—yes—oil spills. Why are some Leptothrix discophora
As a Leptothrix discophora film
discophora film. Hit your browser's back button or the FAQs
link to return to
this page. Why do some
films of Leptothrix
discophora have holes in them?
The holes are places where bubbles of oxygen released by submerged
algae have popped through. Here is a photograph of a Leptothrix
discophora film with
holes in it. Hit your browser's back button or the FAQs link to
to this page.
Sometimes a Leptothrix discophora film lies on
top of an orange pudding-like substance; what is it?
The pudding-like reddish material is probably the product (a
flocculate) of the iron-oxidizing bacterium called Leptothrix ochracea. Here is a
photograph of an L. discophora
film on top of the pudding-like substance. Hit your browser's back
button or the FAQs link to return to this page.
the Vermilion River, when
are iron bacteria found?
In the U.S. they are abundant in the Great Lakes region. They live
around the world in iron-rich aquatic habitats ranging in size from
puddles to oceans. They can
even grow on iron pipes, where they can cause unwanted corrosion. These
bacteria occur everywhere on the planet that
conditions support their growth and possibly on other planets.
Mars is a possible site. Here are photographs of iron bacteria
and in Osprey,
Florida. Hit your browser's back button or the FAQs link to
return to this page.
support their growth?
Four conditions that favor the growth of iron bacteria are: 1) slowly
moving or still water, 2) warm air and water, 3) lack of recent heavy
rainfall, and 4) water that contains little dissolved oxygen. When did this
life form first appear on earth?
Two-and-a-half to three-and-a-half billion
years ago—even before the beginning of green-plant
photosynthesis—some microorganisms acquired the ability to use
certain minerals rather than the sun’s energy to fuel growth and
reproduction. These iron-utilizing
organisms probably rank among the earliest forms of life. Why are iron
Most people can easily ignore the iron bacteria, but ignored or not,
these creatures set in motion an important process that I like to think
of as a loop of eternity: a cycle from nonliving to living matter and
again. Iron, like every chemical element that organisms require,
participates in a biogeochemical cycle that plays through organisms and
the physical media that support them. For iron in the Vermilion River,
movement into the living phase of the cycle begins when bacteria
release the iron from pyrite-bearing shale. The iron dissolves in
water, where plants growing along the river use it as a nutrient.
Herbivores eat the plants, and some of the herbivores become food for
carnivores. When the plants and animals die, bacteria and fungi feed on
their remains, releasing the iron that they accumulated in life back
into the soil or water, where living plants or bacteria eventually
reabsorb it, continuing the cycle.
The bacteria that extract their energy from rock-bound iron in places
like the Vermilion River are not only harmless to humans, but they are
also essential to all other forms of life. If bacteria didn’t
participate in these miraculous biogeochemical cycles, usable forms of
several nutrient metals would be too scarce to sustain other
organisms—indeed, to sustain the living world as we know it. Are there any
practical applications of these kinds of microbes?
Iron bacteria are thought to have concentrated iron into large
formations that have been mined for early human tool making and
continue to be used in the modern steel industry. Some
bacteria are used to extract metals from low-grade ores. Others clean
up acid-mine drainage or convert toxic industrial wastes such as
uranium-contaminated soil and groundwater to more soluble, therefore
more recoverable, forms. Scientists are even experimenting with these
bacteria to build microbial fuel cells. Where can I find
about Leptothrix discophora and
Here are two resources. More can be found by Googling the terms
mentioned on this page of Frequently Asked Questions.
Bacteria,” a chapter from the book Living in the Vermilion River Watershed, Mary
Why do you take photographs?
I take photographs for my own delight, but also to help
others look at their everyday physical surroundings with increased
awareness, respect, and enjoyment of what, previously, they may have
deemed unremarkable. But most of all I
make photographs to affirm the reality of the material world. Taking
photographs is one way I know to get closer to the physical world.
Biologist and naturalist E. O. Wilson uses the term biophilia to
describe humans’ innate love of the biological world; it is only
through this love, Wilson believes, that will we care enough to save
it. My impulse to engage in nature photography is compatible with this
line of thought. I photograph nature with mixed emotions: joy in
focused observation of my
immediate visual field and pain in awareness of the greater context.
Natural environments the world over are being destroyed by human greed,
ignorance, and overpopulation. The bacteria I photograph have not
diminished—indeed, they have thrived for nearly four billion years—but
their setting in verdant foliage and interesting rock formations may not
remain if the pressure of human population on this spot increases much
more. I despair daily over these losses and losses to come, yet, camera
in hand, I continue to search out instances of remaining natural
Still photography—as opposed to motion pictures—is able to record only
a moment. I take pleasure in this fact, and one reason has to do with
aging. As I become older, I have less future, but just as much present;
photography helps me find more incentive to live in the moment.
Photography, which depends on light and exploits its nuances, offers
myriad opportunities to discover the uniqueness of time and place; it
teaches love of the moment and love of the physical world.
you combine photographs with embroidery and drawing?
While I feel I must take and print photographs, photography is not
sufficient to satisfy my desire to make. I want a more sustained and
intense physical relationship with the image. That is why I also print
photographs on cloth and stitch into them. Or I print part of a
photograph on paper and complete a composition with colored pencils. Or
I print separate photographs, transfer them with gel medium to paper,
and finish with drawing. Adding the other media to the work allows me
not only to spend more time with the original image and enjoy a more
tactile experience, but also to explore more fully notions of reality,
representation, and abstraction.
photographs available as prints for purchase?
Yes. Please write
for more information.