物质循环
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Nutrient Cycling: CNS and P
Nutrient Cycling: CNS and P
1. Definition: (Element Cycling, Nutrient Cycling) - the physical movement and chemical transformation of material by biochemical activities throughout the atmosphere, hydrosphere, and lithosphere C, H, O, N, S, P, … Fe, Mo, Mn, etc. 2. Major roles of microorganisms in most element cycles – because of diverse metabolic capabilities ubiquity high rates of enzymatic activity 3. Reservoirs/ pools – stores of elements (mass) e.g. atmosphere, soil, biomass, oceans – all are reservoirs of C 4. Transfer rates/Fluxes – rates of movement of elements between reservoirs (mass per time)
2. Methanotrophs (Methylotrophs) （甲烷氧化菌） Aerobic a. Eubacteria b. use CH4 as their energy source c. CH4 + 2 O2 2 H2O + CO2 d. some can also use other 1-C compounds as energy sources (methanol, formate, CO, others) f. obligate aerobes (O2 is e- acceptor) g. occur in transition zones above methanogens, but where O2 is available, or h. occur in upland soils (non-methanogenic), where atmospheric CH4 is the major energy source Anaerobic a. Archaea, though none yet isolated b. use CH4 as C and energy source? c. much to learn about their biochemistry/ecology
4) Conversions between methane and CO2
Methanogenesis and Methylotrophy 1. Methanogens (产甲烷菌） a. Archaea b. active at very very low redox potentials – 350 to –450 mV c. name means Methano– ‘methane’ (CH4) –genesis ‘production’ d. CO2 is e- acceptor; H2 is energy source (e- donor) e. HCO3- + 4H2 + H+ CH4 + 3 H2O simplified expression; pathway is very complex
The Carbon Cycle
1. ‘Fast’ Cycle – decades or less a. reservoirs: atmosphere, surface oceans, biota, soils b. transfers: photosynthesis, respiration, fossil fuel burning c. Biological processes dominate
Elemental Cycling: definitions
Assimilatory (同化） processes: builds biomass constituents. Dissimilatory（异化） process: reduction coupled to energy (nrg)-yielding oxidation. Mineralization: Conversion from organic to inorganic state. Oxidation: loss of electrons; releases energy.
3) Assimilation and dissimilation
Cellular energy is frequently derived from the oxidation of organic carbon molecules. Carbon can be stored (eg. polyhydroxybutyrate in bacteria; fat in animals) for later oxidation as an energy source. Respiration (oxidation of organic carbon to yield CO2) completes this cycle back to the atmospheric compartment. Total ecosystem photosynthesis and respiration come close to balancing on a global basis.
Food Chain Energetics
Autotrophs: CO2org. C producer higher plants (H2O split; nrg from sun) algae (H2O split; nrg from sun) bacteria (H2O, H2 or H2S split; nrg from sun or chemical oxidations) Heterotrophs: Consumers org. C org. C primary = herbivores secondary = feed on herbivores tertiary = feed on secondary omnivores = feed on combination of producers/ consumers Decomposers (detritivores) org. C less complex org. C CO2 bacteria, fungi
The Nitrogen Cycle
Nitrogen has numerous oxidation states and is involved in complex chemical pathways, some manners of microbial energy production, and the cycling of other elements.
and bacteria
1) Dissowk.baidu.comution and precipitation
CO2 + H2O H2CO3 H+ + CO32- / HCO3Ca2+ + CO32- CaCO3 [insoluble] CaCO3 [insoluble] + CO2 + H2O Ca(HCO3)2 [soluble]
2) Physical exchange
Carbon is physically exchanged as CO2 between the atmosphere, oceans, lakes and streams. Organic carbon or as carbonate can settle into deep sediments and be removed from rapid cycling. If this process occurs over geological time (over 100,000 years) under high pressure and temp, the result is oil or coal (fossil fuel) formation.
Reduction: gain of electrons; requires energy input.
Redox couple: coupling of oxidation and reduction. The net difference in the oxidation and reduction half-reactions provides energy for cell function.
2. ‘Slow’ Cycle – millennia a. reservoirs: deep oceans, sediments, fossil fuels b. transfers: sediment burial, volcanoes c. Geological processes dominate
+500
Eh (meV)
0
-500
-1000
Time
Key nitrogen conversions
Nitrogen fixation - Conversion of dinitrogen gas to ammonium. Nitrification - Conversion of ammonium to nitrate - aerobic bacteria; different species responsible for 2 specific steps in the process. Dissimilatory nitrate reduction – Anaerobic conversion of nitrate to nitrite; bacteria. Nitrate used as electron acceptor to drive energy production. First step in denitrification. Denitrification - Multistep reduction of nitrate to gaseous dinitrogen. Performed by nitrate reductase enzyme system - different bacteria may perform different steps. Numerous intermediates. Nitrate used as electron acceptor to drive energy production.
The Carbon Cycle: 4 main types of processes
1) dissolution and precipitation 2) physical-chemical exchange of carbon between environmental compartments 3) assimilation and dissimilation [photosynthesis, respiration, trophic transfer] 4) conversions between methane and CO2
Simplified Eh Cascade for Alternate e- Acceptors
+1000 O2 + e- H2O NO3 + e- N2 Mn(IV) + e- Mn(II) Fe(III) + e- Fe(II) SO42-+ e- H2S CO2 + e- CH4
Nutrient cycles and energy flow are related. C cycling is most directly related to energy flow.
CO2 + H2O + light nrg CHO + O2 CHO + O2 released nrg + H2O + CO2.
Nutrient Cycling: CNS and P
1. Definition: (Element Cycling, Nutrient Cycling) - the physical movement and chemical transformation of material by biochemical activities throughout the atmosphere, hydrosphere, and lithosphere C, H, O, N, S, P, … Fe, Mo, Mn, etc. 2. Major roles of microorganisms in most element cycles – because of diverse metabolic capabilities ubiquity high rates of enzymatic activity 3. Reservoirs/ pools – stores of elements (mass) e.g. atmosphere, soil, biomass, oceans – all are reservoirs of C 4. Transfer rates/Fluxes – rates of movement of elements between reservoirs (mass per time)
2. Methanotrophs (Methylotrophs) （甲烷氧化菌） Aerobic a. Eubacteria b. use CH4 as their energy source c. CH4 + 2 O2 2 H2O + CO2 d. some can also use other 1-C compounds as energy sources (methanol, formate, CO, others) f. obligate aerobes (O2 is e- acceptor) g. occur in transition zones above methanogens, but where O2 is available, or h. occur in upland soils (non-methanogenic), where atmospheric CH4 is the major energy source Anaerobic a. Archaea, though none yet isolated b. use CH4 as C and energy source? c. much to learn about their biochemistry/ecology
4) Conversions between methane and CO2
Methanogenesis and Methylotrophy 1. Methanogens (产甲烷菌） a. Archaea b. active at very very low redox potentials – 350 to –450 mV c. name means Methano– ‘methane’ (CH4) –genesis ‘production’ d. CO2 is e- acceptor; H2 is energy source (e- donor) e. HCO3- + 4H2 + H+ CH4 + 3 H2O simplified expression; pathway is very complex
The Carbon Cycle
1. ‘Fast’ Cycle – decades or less a. reservoirs: atmosphere, surface oceans, biota, soils b. transfers: photosynthesis, respiration, fossil fuel burning c. Biological processes dominate
Elemental Cycling: definitions
Assimilatory (同化） processes: builds biomass constituents. Dissimilatory（异化） process: reduction coupled to energy (nrg)-yielding oxidation. Mineralization: Conversion from organic to inorganic state. Oxidation: loss of electrons; releases energy.
3) Assimilation and dissimilation
Cellular energy is frequently derived from the oxidation of organic carbon molecules. Carbon can be stored (eg. polyhydroxybutyrate in bacteria; fat in animals) for later oxidation as an energy source. Respiration (oxidation of organic carbon to yield CO2) completes this cycle back to the atmospheric compartment. Total ecosystem photosynthesis and respiration come close to balancing on a global basis.
Food Chain Energetics
Autotrophs: CO2org. C producer higher plants (H2O split; nrg from sun) algae (H2O split; nrg from sun) bacteria (H2O, H2 or H2S split; nrg from sun or chemical oxidations) Heterotrophs: Consumers org. C org. C primary = herbivores secondary = feed on herbivores tertiary = feed on secondary omnivores = feed on combination of producers/ consumers Decomposers (detritivores) org. C less complex org. C CO2 bacteria, fungi
The Nitrogen Cycle
Nitrogen has numerous oxidation states and is involved in complex chemical pathways, some manners of microbial energy production, and the cycling of other elements.
and bacteria
1) Dissowk.baidu.comution and precipitation
CO2 + H2O H2CO3 H+ + CO32- / HCO3Ca2+ + CO32- CaCO3 [insoluble] CaCO3 [insoluble] + CO2 + H2O Ca(HCO3)2 [soluble]
2) Physical exchange
Carbon is physically exchanged as CO2 between the atmosphere, oceans, lakes and streams. Organic carbon or as carbonate can settle into deep sediments and be removed from rapid cycling. If this process occurs over geological time (over 100,000 years) under high pressure and temp, the result is oil or coal (fossil fuel) formation.
Reduction: gain of electrons; requires energy input.
Redox couple: coupling of oxidation and reduction. The net difference in the oxidation and reduction half-reactions provides energy for cell function.
2. ‘Slow’ Cycle – millennia a. reservoirs: deep oceans, sediments, fossil fuels b. transfers: sediment burial, volcanoes c. Geological processes dominate
+500
Eh (meV)
0
-500
-1000
Time
Key nitrogen conversions
Nitrogen fixation - Conversion of dinitrogen gas to ammonium. Nitrification - Conversion of ammonium to nitrate - aerobic bacteria; different species responsible for 2 specific steps in the process. Dissimilatory nitrate reduction – Anaerobic conversion of nitrate to nitrite; bacteria. Nitrate used as electron acceptor to drive energy production. First step in denitrification. Denitrification - Multistep reduction of nitrate to gaseous dinitrogen. Performed by nitrate reductase enzyme system - different bacteria may perform different steps. Numerous intermediates. Nitrate used as electron acceptor to drive energy production.
The Carbon Cycle: 4 main types of processes
1) dissolution and precipitation 2) physical-chemical exchange of carbon between environmental compartments 3) assimilation and dissimilation [photosynthesis, respiration, trophic transfer] 4) conversions between methane and CO2
Simplified Eh Cascade for Alternate e- Acceptors
+1000 O2 + e- H2O NO3 + e- N2 Mn(IV) + e- Mn(II) Fe(III) + e- Fe(II) SO42-+ e- H2S CO2 + e- CH4
Nutrient cycles and energy flow are related. C cycling is most directly related to energy flow.
CO2 + H2O + light nrg CHO + O2 CHO + O2 released nrg + H2O + CO2.