Introduction

This video shows a diverse group of oxygen-evolving soil microorganisms including cyanobacteria, green algae, and diatoms. The cyanobacteria are prokaryotic and have a simpler structure that lacks a membrane-bound nucleus, whereas green algae and diatoms are eukaryotic and have a more complex cellular structure. Both are photosynthetic (producer) organisms that use the energy of sunlight to generate new biomass. Their photosynthetic mechanisms are nearly identical biochemically (and similar to those of higher green plants), which evolve oxygen during photosynthesis. They vary in shape from single-celled, to filamentous, or to diatoms that are covered with a layer composed of silica. Thick deposits of diatom frustules (outer shells) are mined as diatomaceous earth, which is chemically inert and contains about 86-88% silica. Many cyanobacteria (commonly referred to in the past as blue-green algae) fix dinitrogen gas from the atmosphere and make nitrogen available to themselves and other organisms in the environment. This is done in specialized cells called heterocysts, which contain the nitrogenase enzyme that is oxygen labile (destroyed by oxygen). Heterocysts often have thick cell walls to exclude oxygen, while neighboring vegetative cells produce  (the product of photosynthesis) and evolve oxygen.A downloadable, high-resolution version of this video is available at http://www.agron.iastate.edu/~loynachan/mov/.

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Sylvia, D. M., J. J. Fuhrmann, P. G. Hartel, and D. A. Zuberer. 2005. Principles and applications of soil microbiology. Pearson Prentice Hall, Upper Saddle River, NJ.