Iron Oxide Bacteria

In my little village there is a stream that runs into the lake that the village is named for.  One day when I first moved here, I noticed a trail of shimmery, orange sludge leaching into the stream. Initially, I thought (with great concern) that this was coming from some contaminated source, buried in the hillside surrounding the stream, but upon further research and inquiry when I began my pigment project – I came to learn that the source is actually Iron Oxide Bacteria, and thankfully, a naturally occurring substance.  Iron Oxide Bacteria are chemotrophic bacteria that derive the energy they need to live and multiply by oxidizing dissolved ferrous iron. [1]

These harmless bacteria “bloom” when oxygen, water and iron combine. The bacteria are typically rust-colored and appear oily. They form masses composed mainly of the iron oxide-accumulating bacterium Leptothrix. Iron bacteria undergoes an oxidation process (change their compound structure) to fulfill it’s energy requirements. This involves changing ferrous iron (Fe2+) into ferric iron (Fe3+). This process makes the iron insoluble and produces the rust-colored slimy deposit in stream beds. [2]

Iron Oxide Bacteria have been used by hunter gathers in North America’s Pacific Northwest, among other cultures, for use in pigments for rock art, personal adornment and mortuary practices. A research paper by Brandi Lee MacDonald at the University of Missouri, touches on the technological innovation and human evolutionary development of these peoples and their use of heating the iron oxide bacteria to enhance their color and increase their colorfastness for the use of this material as a pigment for rock art. [3]

Even animals have used iron oxide, and iron oxide bacteria as a means of adornment – though the true purpose of why is still unknown. The Bearded Vulture is known to cover decorate itself by covering it’s white chest feathers in iron oxide dust and bathing in pools rich with iron oxide. Research has suggested that this behavior is either an attempt at asserting dominance or as a means of replacing carotenoids, which their bodies do not produce on their own. [4][5]

Iron Oxide Bacteria is a magical and strange substance, and I am thankful to have a seemingly endless source of it in my backyard. I am currently drying some out to crush into pigment to utilize in my artwork and catalog in the archive, and look forward to continued research on cultural uses of this particular source of color throughout the ages. If you have any knowledge to share with regards to Iron Oxide Bacteria use in art/culture, or other environmental information you’d like to share, please do so in the comments. I hope through this crisis we are all dealing with together, that you and yours are and remain healthy and well, and that you are able to use this time in isolation to tap into your creative spirit and find ways to reconnect with our marvelous planet.

 

1. https://en.wikipedia.org/wiki/Iron-oxidizing_bacteria

2. https://adoptastream.georgia.gov/what-iron-bacteria

3. https://www.researchgate.net/publication/337341971_Hunter-Gatherers_Harvested_and_Heated_Microbial_Biogenic_Iron_Oxides_to_Produce_Rock_Art_Pigment

4.https://www.researchgate.net/publication/337341971_Hunter-Gatherers_Harvested_and_Heated_Microbial_Biogenic_Iron_Oxides_to_Produce_Rock_Art_Pigment

5. https://europepmc.org/article/pmc/pmc4730124

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