cyanobacteria and others are symbioac ex rhizobium 20

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Unformatted text preview: ock weathering and other inorganic materials. –  Organic soils: derived from sedimentaAon in bogs and marshes. •  Soils are composed of –  –  –  –  Inorganic mineral maber (~40% of soil volume) Organic maber (~5%) Air and water (~50%) Living organisms 15 Soil Humus: Dead plant material that is resistant to decomposiAon. Keep water and nutrients in the soil. 16 Brock Biology of Microorganisms, 13th EdiAon. Diversity of soil microorganisms 17 Brock Biology of Microorganisms, 13th EdiAon. Soil •  •  •  Most microbial growth takes place on the surfaces of soil parAcles The availability of water is the most important factor influencing microbial acAvity in surface soils –  Sand: water drains quickly –  Silt: retains water to the right extent –  Clay: water retained too well soil becomes anoxic. Nutrient availability is the most important factor in subsurface environments. 18 Brock Biology of Microorganisms, 13th EdiAon. Microorganism in soil •  •  Rhizosphere: soil that surrounds plant roots and receive plant secreAons. Mycorrhizae: associaAon of fungi with plant roots. Top few cenAmeters: –  Bacteria: up to 2.5 x 109 –  Fungi: up to 2 x 105 –  Protozoa: up to 3 x 104 –  Algae: up to 2.5 x 104 Prokaryotes are largely responsible for: –  the producAon of the humus –  release of minerals from soil parAcles (producAon of acids from organic compounds solubilize the minerals) –  cycling of nutrients (C, N,...
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This note was uploaded on 03/20/2014 for the course PSYC 101 taught by Professor Catone during the Spring '07 term at CSU Fullerton.

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