Through their processes including the exusion and release of organic compounds, plant roots are extremely important soil organisms. Algal populations typically range from 10,000 - 100,000 cells per gram of soil. Green algae prefer moist, non flooded acidic soils while diatoms prefer well drained land rich in organic matter. Blue-green algae, Cyanobacteria, are prokaryotes and are usually classified as bacteria Soil Algae contain chlorophyll enabling them like plants to carry out photosynthesis if exposed to light and moisture. They produce substantial O.M in some fertile soils and certain algae excrete polysaccharides which increase soil aggregation.
Yeasts are single celled organisms that live mainly in waterlogged anaerobic soils.
Soil Fungi have plant like eukaryotic cells but no capacity for photosynthesis. They depend on living or dead OM for carbon and energy and, especially the molds, play a very important role in the transformation of soil constituents. Mushrooms prefer moist conditions rich in organic matter, as associated with forest and grass vegetation. In addition to the above ground fruiting body an extensive system of hyphae permeate the soil and play an important role in the breakdown of OM and woody tissue. Molds play a much more important role in soils than mushroom fungi and predominate in acid surface soils, where bacteria and actinomycetes offer only mild competition.