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Chapter 27

Chapter 27 . Environmental Microbiology. Metabolic Diversity. Microbes live in the most widely varied habitats on Earth due to metabolic diversity dynamic associations occur between microbes and ecosystem Extremophiles Most are Archaea

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Chapter 27

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  1. Chapter 27 Environmental Microbiology

  2. Metabolic Diversity • Microbes live in the most widely varied habitats on Earth • due to metabolic diversity • dynamic associations occur between microbes and ecosystem • Extremophiles • Most are Archaea • Produce specialized enzymes (extremozymes) that allow them to tolerate extreme conditions

  3. Microbes live in an intensely competitive environment • High biodiversity • Competitive exclusion • Live in symbiotic relationships • Ruminants • Mycorhizae

  4. Endomycorrhiza Ectomycorrhiza

  5. Soil Microbiology • Billions of organisms in soil • Over 80 % are bacteria • Millions in each gram of soil • Most are in the top few centimeters of soil • Biomining • Many antibiotics come from Actinomycetes • Streptomycin, tetracycline • Bacterial populations estimated by plate count

  6. Biogeochemical cycles for carbon, nitrogen, sulfur and phosphorus are vital for life • Elements oxidized and reduced by microbes to meet their metabolic need • Recycles elements into the environment • Production • Consumption • Decomposition

  7. The Carbon Cycle • All organisms contain large amounts of carbon • Autotrophs fix CO2 into organics • 1st step of carbon cycle • Heterotrophs consume autotrophs • 2nd step of carbon cycle • Carbon reenters the environment as CO2 • due to respiration; decomposition by microbes; burning fossil fuels • Global warming

  8. The Nitrogen Cycle • Nitrogen is needed for synthesis of proteins and nucleic acids • Deamination • amino groups are removed and converted to ammonia • Ammonification • release of ammonia

  9. Nitrification • oxidation of ammonium into nitrate • nitrate can be fully oxidized and used as an electron acceptor • Denitrification • leads to loss of nitrogen back to the atmosphere as nitrogen gas • Pseudomonas species are the most important soil denitrifying bacteria • Occurs in waterlogged soils where little oxygen is available

  10. Nitrogen Cycle Microbial decomposition Proteins and waste products Amino acids Microbial ammonification Amino acids (–NH2) Ammonia (NH3) Nitrosomonas Ammonium ion (NH4+) Nitrite ion (NO2- ) Nitrobacter Nitrite ion (NO2-) Nitrate ion (NO3- ) Pseudmonas Nitrate ion (NO3-) N2

  11. Nitrogen makes up ~ 80% of the Earth’s atmosphere • Exists as nitrogen gas (N2) • Must be fixed into usable form • Specific microbes important in this conversion • Nitrogen fixation requires nitrogenase • Deactivated by oxygen Nitrogen - fixation N2 Ammonia (NH3)

  12. Two types of nitrogen fixers: • Free-living • found in rhizosophere • Aerobic species - Azotobacter and Beijerinckia • Cyanobacteria –heterocysts • Anaerobic species - Clostridium

  13. Symbiotic • Rhizobia form root nodules on legume plants • Frankia associated with alder trees • Lichens when containing a cyanobacteria • Cyanobacteria & Azolla in rice patty water

  14. The Sulfur Cycle • Involves numerous oxidation states • Most reduced forms are sulfides like H2S gas • Generally forms under anaerobic conditions • Source of energy for some autotrophic bacteria • Convert reduced sulfur in H2S into elemental sulfur and oxidized sulfates • Thiobacillus • Endoliths

  15. Winogradsky studied filamentous aquatic bacteria Beggiatoaalba • Revealed much about bacterial sulfur recycling and chemoautotrophy • Primary producers in deep ocean and endolithic communities are chemoautotrophic bacteria

  16. Several photo-autotrophic bacteria use light for energy and use H2S to reduce CO2 • Sulfates are incorporated into plants, animals and bacteria as disulfide bonds in proteins • Proteins decompose; sulfur released as H2S • Dissimilation

  17. Sulfur Cycle Microbial decomposition Proteins and waste products Amino acids Microbial dissimilation Amino acids (–SH) H2S Thiobacillus H2S SO42– (for energy) Microbial & plant assimilation SO42– Amino acids Desulfovibrio SO42– H2S (reduced)

  18. The Phosphorus Cycle • Limiting factor for plant and animal growth • Exists primarily as phosphate ion (PO43-) • Little change during oxidation • soluble to insoluble; organic to inorganic • Often related to pH • Can be solubilized in rock by acids produced by bacteria like Thiobacillus

  19. There is no product to return it to atmosphere • Accumulates in sea; certain islands are mined for phosphate deposits • Used in detergents and fertilizers • Runoff may lead to eutrophication

  20. The Phosphorous Cycle

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