Soil 120: Introduction to Soil Microbiology (PDF)

SOIL 120 Introduction to Soil Microbiology Nolissa D. Organo How many organisms are there in a handful of soil? Three hundred? Four hundred million? One million? One thousand? Eight million?...

SOIL 120 Introduction to Soil Microbiology Nolissa D. Organo How many organisms are there in a handful of soil? Three hundred? Four hundred million? One million? One thousand? Eight million? Sixty-five million? There are more living organisms in a handful of soil than there are people on earth.  If you were to walk out into a mature forest or a farm where the soil was being well-managed, gather a handful of soil, and put it under a microscope, here’s what you might see: 10-50 billion aerobic bacteria Up to 100 million different fungal cells Hundreds or thousands of arthropods and micro-arthropods Thousands of different algae, protozoa, and nematodes. https://www.growjourney.com/five-amazing-soil-facts-will-change-way-view-world Questions: What/who are these soil microorganisms? Why are there so many soil organisms? What roles do they play in the soil? Why are they important? What are the applications in agriculture and environmental problems? Soil Microbiology It is a branch of science/microbiology which deals with the study of soil microorganisms and their activities in the soil. Applications to agriculture. Overview of Soil Biology Soil organisms Classification of soil organisms Soil Organisms Creatures that spend all/part of their lives in the soil environment.  Classification of soil organisms 1. Based on size 2. Based on metabolism 3. Based on ecological function 4. Based on hierarchy in the soil food web 5. Based on phylogeny 1. Classification based on Size Megafauna: size range - 20 mm upward, e.g. moles, rabbits, and rodents. Macrofauna: size range - 2 to 20 mm, e.g. woodlice, earthworms, beetles, centipedes, slugs, snails, ants, and harvestmen. …based on Size Mesofauna: size range - 100 micrometres to 2 mm, e.g. tardigrades, mites and springtails. Microfauna and Microflora: size range - 1 to 100 micrometres, e.g. bacteria, actinomycetes, fungi, protozoa. 2. Classification based on Metabolism Autotrophs Primary producers "self-feeding", from the Greek words, “autos” (self) and “trophe” (nourishing). Organisms that obtain their C mainly from CO2 Photoautotrophs – obtain energy from sunlight (photosynthesis). Chemoautotrophs - obtain energy from the oxidation of various elements. …based on Metabolism Heterotrophs From the Greek words, “heteros” (another, different) and trophe (nutrition). Organisms incapable of making their own food from light or organic compounds. Feed on organisms or remains of other organisms to get their necessary energy to survive. 3. Classification based on Ecological Function Herbivores - subsist on living plants. Detritivores - subsist on dead plant debris. Predators - consume animals. Parasites - live off, but do not consume other organisms. Mutualists – in a symbiotic relationship. 4. Based on hierarchy in the soil food web Food webs describe the transfer of energy between species in an ecosystem. SOIL FOOD WEB – describes the transfer of energy between soil organisms. Classifies organisms based on their trophic level. Classification based on the soil food web Source: http://www.nrcs.usda.gov/Internet/FSE_MEDIA/nrcs142p2_049822.jpg 5. Classification based on phylogeny Based on the evolutionary relationship between organisms. Adds a level of classification "above" the kingdoms, called Domains (Three-domain system). Reflected in the organism’s ribosomal DNA (rDNA). Classification based on phylogeny Two main divisions: Eukaryotic organisms – presence of a true nucleus that is enclosed in a nuclear envelop. Eukaryotic organisms belong to the domain Eukarya. Prokaryotic organisms – absence of a true nucleus. The DNA is stored in an area termed as “nucleoid.” Prokaryotic organisms may belong to either the domain Bacteria or domain Archaea. Classification based on phylogeny Evolutionary tree showing the common ancestry of all three domains of life. How to perform Phylogenetic Analysis? Laboratory Activities Sequence Result Blast Search Phylogenetic Analysis Next lecture topic The Cell