Life’s distant echos

One of the many highlights of Frijoles Canyon in Bandelier National Monument is the little Rito Frijoles – a bright thread of water winding its way down from the volcanic domes in the northwestern highlands of the park to the Rio Grande on the east. Except in storm, its waters are clear, or perhaps very slightly clouded with tannin released into the water from the Ponderosa pine duff along its banks.

The bed of Frijoles Creek is paved with fragments of lava and tuff, rounded by flash floods. A sandy drift fills in among the cobbles, and when the sun shines into the shallow ripples you can see the soft, luminous, butterfly-blue glint of clear feldspar crystals sending back the light. Deer come down to drink beneath the cottonwoods and pines.

But I want to draw your attention to a less attractive, but remarkably significant, play of light on the water: an oily sheen – sometimes called the iron slick – obscuring the water flowing over an ugly rusty slime coating the pebbles and twigs on the creek bed.


These are the tell-tale signs of an active colony of the iron-oxidizing bacteria Leptothrix, rusting the slightly acidic, iron-bearing water seeping out of the stream side. Leptothrix is a distant echo from our planet’s truly distant past, a primitive life form predating other kinds of plants or animals we might recognize from the fossil record. Leptothrix uses chemosynthesis, not photosynthesis, to satisfy its hunger, oxidizing traces of iron for energy and discarding microscopic sheaths of rust as slimy waste. It seems more like an infection from an alien world than a healthy member of the modern ecology.

But to my thoughts the dazzling thing is that here is a fundamental organism that hasn’t died for perhaps a billion years, reproducing by fission, disdaining the sun, reporting the news of the Proterozoic Era, still eking out a living in damp seeps all around the Earth.


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