Sunday, March 10, 2019

A view of microbial life in soil

Image source

All soils teem with microscopic life that is invisible to the naked eye, and for that reason often overlooked. Yet, microorganisms are an essential component of all soils, and through their metabolic activity (mineral weathering, production and recycling of organic matter, and more) soil microbes actually play a major role in soil formation, development, and fertility.

The images presented here show diverse microorganisms inhabiting a pasture soil. I sampled this soil on the Uetliberg, in Zürich, Switzerland, in 2018. Samples were chemically fixed and observed with scanning electron microscopy. Post-acquisition pseudocoloring was applied to the images - in other words, colors were added to the original black and white images to facilitate visualization of the microbes and soil particles. (The pseudocolors do not represent the real colors of the samples.)

All images are courtesy of the Soil and Terrestrial Environmental Physics group of Dani Or at ETH Zurich. SEM image acquisition and coloring by Anne Greet Bittermann, ETH Zurich - ScopeM.

We do not know the precise identity of these microbes (we would need DNA sequencing for that), but given their shape and size some level of characterization is possible. Most of them are bacteria, which are the most abundant cellular organisms in all soils.

Scanning electron microscopy reveals the complex arrangements of bacterial cells and soil particles with a great level of details. The colored filaments are likely remnants of extracellular polymeric subtances connecting cells and soil together.

Those images (and more) can be downloaded from our image gallery.  

For those interested in soil microbial life, we published an open access review on that topic in the journal FEMS Microbiology Reviews.

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