MMG301 1nd Edition Lecture 28Outline of Last Lecture I. Microbes Outline of Current Lecture II. Soil microbiologyIII. Plant microbe interactionsCurrent Lecture-Solids consist of soil separates (sand, silt, and clay) & soil organic matter.-A soil aggregate of -Solids (mineral and organic components)-Liquids-Gases -Most microbes are in microcolonies on soil particles. -Soil aggregates contain many microhabitats suitable for microbial growth-Clays are the major inorganic soil separate affecting microbial activity in soil-Their size £ bacteria, are the greatest surface area component, affect ion /nutrient mobility, buffer pH, water retention, porosity and gas exchange-Fermentative end products of microbial anaerobic metabolism found even in sandy, well-drained soils.-O2 diffusion is restricted, so anoxic microenvironments develop within their interior of soil aggregates, where microbes are still actively conducting anaerobic fermentative metabolism.-Microbes in discontinuous water films on the surface of soil particles have good access to O2. -In contrast, microbes in continuous water-filled pores have limited O2 fluxes, creating anoxic microenvironments. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Plants secrete various organic compounds resulting in a nutritionally enriched environment favorable for microbial growth -As a result, plants are heavily colonized with a diversity of microorganisms whose reservoir is primarily the soil.-Microbes that colonize plants are called either epiphytes (colonize plant surface) or endophytes(colonize plant interior) -Phyllosphere: aerial leaf surface of plants-Communities of microorganisms that develop on the phyllosphere are adapted to tolerate high irradiation and low humidity stresses-Many phyllosphere microorganisms antagonize airborne pathogens thereby protecting the plant. -Rhizosphere: region adjacent to the root-Rhizoplane: the root
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