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Microbes in the environment F2, p. 304
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Microbes in ecosystems F.2.1, p. 304
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Did you know? Just one gram of soil contains 5000 to 7000 different species of bacteria. –http://www.buzzle.com/articles/facts-about- the-soil.html
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Good news! You only have to know 5!
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Bacteria Play several major roles in different nutrient cycles –Both in land and in water Involved in P, S, C and N cycles
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Decomposing Bacteria break down dead organisms Nutrients released –Nutrients return to the environment
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Producers Use raw energy (Ex: sunlight) to create organic molecules and nutrients –Used by bacteria and other organisms Includes: –Photosynthetic bacteria (cyanobacteria) –Chemosynthetic bacteria (in the nitrogen cycle)
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Nitrogen cycle F.2.2, p. 304
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Fig. 55-14c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria
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Nitrogen cycle Nitrogen moves through the environment Major reserves are: –Atmosphere –Living things Nitrogen must go through chemical reactions during the cycle
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Nitrogen Comes in two forms: –Pure element, N 2 (gas) –Fixed (as part of a compound)
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Atmospheric nitrogen N 2, gas Three covalent bonds between the atoms –Very difficult to break –Not reactive –Very few organisms have the enzyme for breaking the triple bond Cant be used by organisms
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Fixed nitrogen Nitrogen as part of a compound –Nitrite (NO 2 - ), nitrate (NO 3 - ), ammonium (NH 4 + ) NO 3 -, nitrate, is essential for all organisms –An important part of DNA and protein
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Importance of nitrogen fixing bacteria Where do animals get nitrogen from? –Plants, amino acids, DNA Where do plants get nitrogen from? –NOT the atmosphere –Usually NO 3 -, NH 4 +, which is created by bacteria ALL organisms get fixed nitrogen from bacteria
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Nitrogen fixation p. 304-305
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Nitrogen fixation Nitrogen is fixed by: –Lightening –Manufacturing –Microbes
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Lightening High temperatures cause N 2 and O 2 to combine A series of reactions creates NO 3 - P. 304
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Haber process N 2 and H 2 reacted at high pressure and temperature NH 3 (ammonia) produced Used to manufacture plant fertilizer –Mixed with the soil for plant nutrition
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Microbes fixing nitrogen Two examples: –Azotobacter Free-living –Rhizobium Live in plant root nodules
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Root nodules Mutualistic relationship –The plant gets fixed nitrogen –The bacteria get an anaerobic environment
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Microbial nitrogen fixation N 2 --> NH 3 Requires ATP Azobacter (free living) and Rhizobium (Root nodules) fix nitrogen –Have nitrogenase, the enzyme that fixes N –Breaks the strong N 2 triple bond to produce NH 3
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Fig. 55-14c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria
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Nitrification and denitrification F.2.4, p. 305
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Nitrification Two steps: –NH 3 --> NO 2 - –Ammonia --> Nitrite Nitrosomonas bacteria –NO 2 - --> NO 3 - –Nitrite --> Nitrate Nitrobacter bacteria Releases energy Occurs quickly
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Fig. 55-14c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria
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NO 3 - uses NO 3 - assimilated by plants –Pumped into root hairs by active transport Passed on to animals/heterotrophs through the food chain Used for amino acids/proteins and DNA
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Denitrification NO 3 - --> N 2 + H 2 O Example: Pseudomonas denitrificans Anaerobic respiration –NO 3 - is the electron receptor instead of O 2 Anaerobic soils encourage denitrification –Bad drainage/flooding causes –Denitrification exacerbates the problem
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Fig. 55-14c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria
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Ammonification Also called putrification –Organic matter (feces and dead organisms) are decomposed by bacteria The nitrogen in the organisms is converted into ammonia (NH 3 ) –The NH 3 then goes through nitrification
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Fig. 55-14c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria
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Nitrogen Cycle
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Name each process: Name the bacteria carrying out each process
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Sewage and fertilizer waste F.2.5, p. 305
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Sewage Household - Feces, kitchen waste Industrial - chemicals, heavy metals Farm - fertilizers All cause water pollution –Radically change the aquatic environment
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Downstream pollution Graph on p. 306
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Downstream pollution Table on p. 306
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Steps for contamination 1.Waste discharged, eutricifation 2.Algea bloom, then die off 3.Decomposers break down dead algae and use up oxygen. Oxygen levels decrease. 4.Extreme cases: Oxygen levels are too low and fish/aquatic life is killed (hypoxic zone) 5.Dead organisms are broken down, using oxygen and creating a high concentration of nutrients (eutrification) 6.Extreme cases: nutrients cause another algae bloom, cycle repeats
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BOD Biochemical oxygen demand The level of oxygen in a water sample is recorded over 5 days Less oxygen = More O 2 demand (BOD) = more microbes = more contamination –The contamination feeds the microbes –The microbes demand oxygen
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BOD levels If BOD is too high, fish and other organisms might die –Not enough O2 in the water –oxygen sag Caused by decomposing bacteria –Use up O2
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Oxygen Sag
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Stopping the cycle When the pollutants are broken down and diluted enough, the river can recover –Several kilometers from source of pollution Key: improving oxygen levels, avoiding fish kills
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Sewage treatment F.2.6, p. 307/145
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Treating raw sewage Bacteria are used to treat harmful/polluting substances Two kinds: –Trickle filter bed p. 145 SG –Reed bed. 145 SG
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Biofuels F.2.7, p. 308
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Gasohol Gasoline + ethanol Ethanol comes from yeasts digesting sugar –Sugar from sugar can/sugar beets
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Fig. 27-22c (c)
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Biomass Some microbes convert biomass to fuel –Biomass = Total mass of the living material in an area, minus water –Measured in kg/m 2 –Usually refers to plants
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Biogas Bacterial fermentation Biomass --> CH 4, methane, natural gas Several species of bacteria used together
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Methanognesis F.2.8, p. 308
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Acetogenesis Aerobic bacteria break down waste into lipids, proteins, fats Oxygen used up Acetogenic bacteria (anaerobic) produce acetate
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METHANOGENESIS Acetate converted into CH 4 Uses methanogens (archaea) –Obligate anaerobes –Occurs in a sealed tub
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Advertisements In groups, create illustrated advertisements for the following products: 1.Trickle-filter bed 2.Reed-filter bed 3.Gasohol 4.Biogas/CH 4
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Advertisements: Include the following Target audience/demographic A diagram of the process and equipment Important reaction equations involved The bacteria involved in each process –Include specific environment conditions (ex: anaerobic tank) The benefits of the product/process
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