Linda Grashoff

Photography, Drawing, and Embroidery
Honoring the Physical World

especially the iron bacterium Leptothrix discophora

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Frequently Asked Questions

What is Leptothrix discophora?

What are iron bacteria?

Do bacteria live on other metals besides iron?

How many different kinds of mineral-utilizing bacteria exist?

How many different kinds of iron bacteria live in Ohio's Vermilion River?

Are these microbes dangerous or polluting?

How can you tell the difference between an oil slick and a film of Leptothrix discophora

What accounts for the colors in a Leptothrix discophora film?

Why are some Leptothrix discophora films puckered?

Why do some films of Leptothrix discophora have holes in them?

Sometimes a Leptothrix discophora film lies on top of an orange pudding-like substance; what is it?

Besides in the Vermilion River, when and where are iron bacteria found?

What conditions support their growth?

When did this life form first appear on earth?

Why are iron bacteria important?

Are there any practical applications of these kinds of microbes?


Where can I find more information about Leptothrix discophora and similar bacteria?

How did you learn about the science of these bacteria? Why do you take photographs?

Any other reasons?

Any more?

Why do you combine photographs with embroidery and drawing?

Are your photographs available as prints for purchase?





 


What is 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 browser's back button or the FAQs link to return to this page.

What are iron bacteria?

Iron bacteria are bacteria that use iron to maintain their life functions.  A few examples of iron bacteria are Leptothrix discophora, Leptothrix ochracea, Gallionella ferruginea, and Toxothrix trichogenes. L. discophora's iridescent film can 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 browser's back button or the FAQs link to return to this page.

Do bacteria live on other metals besides iron?

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 many different kinds of mineral-utilizing bacteria exist?

Worldwide, scientists have identified thousands of mineral-utilizing bacteria.

How many different kinds of iron bacteria live in Ohio's Vermilion River?

Perhaps only about 50 kinds of iron bacteria live in the Vermilion River and on the minerals in the river rocks.

Are these microbes dangerous or polluting?

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 discophora film?

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 films puckered?

As a Leptothrix discophora film ages, its chemical composition changes. In essence, it dries out. Having less water in its composition causes the puckering. Here is a photograph of a puckered L. 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 return 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.

Besides in the Vermilion River, when and where 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 in Tokyo and in Osprey, Florida. Hit your browser's back button or the FAQs link to return to this page.

What conditions 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 bacteria important?

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 back around 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 mineral-utilizing 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 more information about Leptothrix discophora and similar bacteria?

Here are two resources. More can be found by Googling the terms mentioned on this page of Frequently Asked Questions.

Finding Beauty in Bacteria,” a chapter from the book Living in the Vermilion River Watershed, Mary C. Garvin and Jan Cooper, editors.

What's the Red in the Water? What's the Black on the Rocks? What's the Oil on the Surface?: How to Collect and See the Microbial Community that Fixes Iron and Manganese in the Natural Environment

How did you learn about the science of these bacteria?
I talked and corresponded with Drs. Eleanora Robbins, a biogeologist, and David Benzing, a biologist, who generously responded to my questions. (Any scientific errors made in depicting the information on this website, however, are all mine.)

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.

Any other reasons?
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 beauty.

Any more?
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.

Why do 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.

Are your photographs available as prints for purchase?
Yes. Please write for more information.


Copyright 2011 Linda Grashoff