vorholt-4
DESCRIPTION
44TRANSCRIPT
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark
752-4001-00L Mikrobiologie
Julia Vorholt Lecture 9: Phototrophy and autotrophy Global carbon and nitrogen cycles Nov 19, 2012
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark
1) Nutrients and microbial growth 2) Introduction to principles of metabolism 3) Chemoorganotrophy 4) Chemolithotrophy 5) Phototrophy 6) Autotrophy, nitrogen fixation 7) Global carbon, nitrogen, sulfur cycles
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Photophosphorylation and ETP
ELQ = h c NA -1 = h v ELQ, Free energy of light quanta h, Planck constant (6.6 x 10-34 J s) c, the speed of light (3 x 108 m s-1) NA, Avogadros number (6 x 1023) v, frequency
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Types of Photosynthesis
PS I and II PS I or II
Van Niel, 1930: Photosynthesis CO2 + 2 H2A -> [CH2O] + 2 A + H2O
Chap. 13.1 Fig. 13.2
Phototrophs
Anoxygenic Oxygenic
Purple and green bacteria Cyanobacteria, algae, green plants
Reducing power Carbon Energy Reducing power Carbon Energy
electrons Light Light
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Groups of Phototrophs
GreenNonsulfur-bacteria
GreenSulfur-
bacteria
Cyanobacteria
Heliobacteria
Purple bacteria (Proteobacteria) Purple Sulfur Bacteria
Purple Nonsulfur Bacteria
(Gram +)
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Evolutionary Aspects
Sunlight represents the most important energy source on earth. Phototrophs use light as sole energy source. They are the starting point of the food chain. The oxygenic photosynthesis evolved rather early in evolution, 2.7 billion years ago. => major consequences in terms of primary biomass production (unlimited availability of H2O) and the presence of O2.
Fig. 16.6
Metabolic highlights
O2 level BYA Eon Organisms,
events
Phanaerozoic
Proterozoic
Archaean
Hadean
Cambrian
Precambrian
Anoxic
Extinction of the dinosaurs
Early animals
Multicellular eukaryotes
First eukaryotes with organelles
Ozone shield
Great oxidation event
Cyanobacteria
Purple and green bacteria
Bacteria/Archaea divergence
First cellular life; LUCA Formation of
crust and oceans Formation of Earth 4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
20%
10%
1%
0.1%
Endosymbiosis?
Aerobic respiration
Oxygenic photosynthesis (2H2O O2 4H) Sulfate reduction
Fe3 reduction Anoxygenic photosynthesis
Acetogenesis
Methanogenesis
Sterile Earth
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Chlorophylls and Bacteriochlorophylls
Organisms must produce some form of chlorophyll (or bacteriochlorophyll) to be photosynthetic
Chlorophyll is a porphyrin They are part of the reaction center (participate directly in the conversion of light
energy to ATP) Number of different types of chlorophyll exist with different absorption spectra
Chap. 13.2 Fig. 13.3
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Carotenoids and Phycobilins
Phototrophic organisms have accessory pigments in addition to chlorophyll, including carotenoids
Carotenoids Always found in phototrophic organisms Typically yellow, red, brown, or green Energy absorbed by carotenoids can be transferred to a
reaction center Prevent photo-oxidative damage to cells
Chap. 13.3 Fig. 13.8
-carotene
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Anoxygenic Photosynthesis
Anoxygenic photosynthesis is found in at least four phyla of Bacteria
Electron transport reactions occur in the reaction center of anoxygenic phototrophs
Reducing power for CO2 fixation comes from reductants present in the environment (i.e., H2S, Fe2+, or NO2-)
Chap. 13.4 Fig. 17.2 Fig. 17.6
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Arrangement of Light-Harvesting Chlorophylls
RC, reaction center LH, light harvesting molecules
Chap. 13.2 Fig. 13.6
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Structure of Reaction Center in Purple Bacteria
Arrangement of Pigment Molecules in Reaction Center
Molecular Model of the Protein Structure of the Reaction Center
Chap. 13.4 Fig. 13.13
1988, Nobel prize for the structure of the reaction center of Rhodopseudomonas viridis: J. Deisenhofer, H. Michel, and R. Huber
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Electron Flow in Anoxygenic PS in a Purple Bacterium
Chap. 13.4
Fig. 13.14
Strong electron
donor
Poor electron
donor
1.0
0.75
0.5
0.25
0.0
0.25
0.5
(V) E0
Cyclic electron flow (generates proton motive
force)
Red or infrared light
External electron donors (H2S, S2O32-,
S0, Fe2+)
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Arrangement of Protein Complexes in Reaction Center
Chap. 13.4 Fig. 13.15
Photosynthetic membrane
Light Out (periplasm)
In (cytoplasm) ATPase
Quinone pool
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Electron Flow in Purple, Green, Sulfur and Heliobacteria
Chap. 13.4 Fig. 13.17
PSII PSI PSI
Purple bacteria Green sulfur bacteria Heliobacteria
Reverse electron
flow
Light Light Light
1.25
1.0
0.75
0.5
0.25
0 0.25
0.5
E0 (V)
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Electron Flow in Oxygenic Photosynthesis
Chap. 13.5 Fig. 13.18 Photosystem II
Photosystem I
The Z Scheme:
Light
Light
PSII PSI
Cyclic electron flow (generates proton motive
force)
Noncyclic electron flow (generates
proton motive force)
1.25
1.0
0.75
0.5
0.25
0.0 E0 (V)
0.25
0.5
0.75
1.0
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Oxygenic Photosynthesis
Oxygenic phototrophs use light to generate ATP and NADPH
The two light reactions are called photosystem I and photosystem II
Z scheme of photosynthesis Photosystem II transfers energy to photosystem I
ATP can also be produced by cyclic photophosphorylation
Chap. 13.5
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Water blooms in lakes consisting of Cyanobacteria
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Autotrophic CO2-fixation
6 different CO2 fixation pathways are known: 1. Calvin-Benson-Bassham cycle 2. Reductive citric acid cycle 3. Reductive acetyl-CoA pathway 4. 3-Hydroxypropionate/malyl-CoA cycle 5. 3-Hydroxypropionate/4-hydroxybutyrate cycle 6. Dicarboxylate/4-hydroxybutyrate cycle
CO2 + 4 [H] + n ATP -> (CH2O) + H2O + n ADP + n Pi
Chap. 13.12-13
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Calvin Cycle
Fixes CO2 into cellular material for autotrophic growth
Requires NADPH, ATP, ribulose bisphophate carboxylase (RubisCO), and phosphoribulokinase
6 molecules of CO2 are required to generate one molecule of glucose
Chap. 13.12 Fig. 13.30
3-Phospho-glycerate(36 carbons)
12
1,3-Bisphospho-glycerate(36 carbons)
12
Glyceraldehyde3-phosphate(36 carbons)
12
Glyceraldehyde3-phosphate(30 carbons)
10
Ribulose5-phosphate(30 carbons)
6
Ribulose1,5-bisphosphate(30 carbons)
6
Fructose6-phosphate(6 carbons)
To biosynthesis
RubisCO
Phosphoribulokinase
Sugarrearrangements
Overall stoichiometry:6 CO2 12 NADPH 18 ATP C6 H12 O6(PO3 H2) 12 NADP 18 ADP 17 Pi
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Nitrogenase and Nitrogen Fixation
Only certain prokaryotes can fix nitrogen Some nitrogen fixers are free living and others are symbiotic
Reaction is catalyzed by nitrogenase Sensitive to the presence of oxygen
A wide variety of nitrogenases use different metal cofactors, usually molybdenum
Pyruvate
Products
Flavodoxin(Oxidized)
Pyruvate flavodoxinoxidoreductase
CoA
Dinitrogenasereductase
(Reduced)
(Oxidized)Dinitrogenase
Flavodoxin
Dinitrogenasereductase
(Reduced)
(Oxidized)
Dinitrogenase
(Reduced)
Acetyl-CoA CO2
Nitrogenaseenzyme
complex
Nitrogenasesubstrates
Overall reaction
Chap. 13.14
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Symbiotic Nitrogen Fixation
Soy bean
without with Bradyrhizobium
(Alphaproteobacterium)
Root nodules
N2 NH3
Chap. 25.3 (Fig. 25.7)
Fig. 25.8
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Symbiotic Nitrogen Fixation
The mutalistic relationship between leguminous plants and nitrogen-fixing bacteria is one of the most important symbioses known
Examples of legumes include soybeans, clover, alfalfa, beans, and peas
Rhizobia are the most well-known nitrogen-fixing bacteria engaging in these symbioses
Chap. 25.3
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Key terms Metabolism - I
We need to distinguish between energy sources and carbon sources (both are usually identical for chemoorganotrophic organisms) Chemotrophy (energy from chemical substrates) > Chemoorganotrophy (organic substrates) > Chemolithotrophy (inorganic substrates)
Phototrophy (energy from light)
Autotrophy (CO2 as main carbon source) Heterotrophy (organic compounds as main carbon source)
Carbon sources
Energy sources
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Key terms Metabolism - II
Aerobic: Growth of an organism using oxygen as electron acceptor Anaerobic: Growth of an organism not using oxygen as electron
acceptor Aerotolerant: Anaerobic organism whose growth is not inhibited by
oxygen and does not use it as electron acceptor
Oxic: Environmental condition where oxygen is present Anoxic: Environmental condition without oxygen
Oxygenic: Type of photosynthesis, oxygen is released from water Anoxygenic: Type of photosynthesis, without oxygen release
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Carbon Cycle and Major Carbon Reservoirs on Earth
Chap. 24.1 Fig. 24.1
Carbon is cycled through all of Earths major carbon reservoirs, i.e., atmosphere, land, oceans, sediments, rocks, and biomass
Humanactivities
Biological pump
Death andmineralization
Respiration
CO2
CO2
CO2
Landplants
Aquaticplants and
phyto-plankton
Animals andmicroorganisms
Fossilfuels
Humus
Soil formation
Earths crust Rock formation
Aquaticanimals
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Methane hydrate
Pictures by K. Kvenvolden and GEOMAR
A methane hydrate is a cage-like lattice of ice, inside of which are trapped molecules of methane.
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark
CO2
(CH2O)n
Oxisch
Anoxisch CH4
Aerobe Atmung (Chemolithotrophe)
Cyanobakterien Pflanzen
Tiere, verschiedene
Mikroorganismen (Paracoccus, E. coli)
Aerobe Methanoxidation
Anaerobe Methanoxidation
Oxygene Photosynthese
(CH2O)n
Anaerobe Atmung Anoxygene
Photosynthese
Purpurbakterien
E. coli Paracoccus denitrificans
Methanogenese
Chap. 24.1 (Fig. 24.2)
The Carbon Cycle
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark
Assimilation/Baustoffwechsel
Aerober Prozess
Anaerober Prozess Dissimilation/
Energiestoffwechsel
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Carbon Cycle
Phototrophic organisms are the foundation of the carbon cycle CO2 is fixed primarily by photosynthetic land plants and marine
microbes CO2 is returned to the atmosphere by respiration of animals and
chemoorganotrophic microbes as well as anthropogenic activities Microbial decomposition is the largest source of CO2
released to the atmosphere The carbon and oxygen cycles are intimately linked Plants dominant phototrophic organisms of terrestrial
environments The two major end products of decomposition are CH4 and CO2
Chap. 24.1
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark
NH3 N2
N2O
Org. N (NH2-Gruppen
N2-Fixierung Rhizobien Cyanobakterien
Nitrifikation Denitrifikation Pseudomonas
Paracoccus
Ammonifikation E. coli
The Nitrogen Carbon Cycle
NO3-
NO2-
NO Nitrosobakterien
(z.B. Nitrosomonas)
Nitrobakterien (z.B. Nitrobacter)
Chap. 24.3 (Fig. 24.7)
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Nitrogen Cycle
Chap. 24.3 Fig. 24.7
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Nitrogen Cycle
N2 is the most stable form of nitrogen and is a major reservoir The ability to use N2 as a cellular nitrogen source
(nitrogen fixation) is limited to only a few prokaryotes Denitrification is the reduction of nitrate to gaseous nitrogen
products and is the primary mechanism by which N2 is produced biologically
Ammonia produced by nitrogen fixation or ammonification can be assimilated into organic matter or oxidized to nitrate
Denitrification and anammox result in losses of nitrogen from the biosphere
Chap. 24.3
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Brock Biology of Microorganisms, Twelfth Edition Madigan / Martinko / Dunlap / Clark
Chemolithotrophe S-Oxidation
Dissimilatorische Sulfatreduktion
Desulfovibrio
Photolithotrophe
Beggiatoa
Schwefel- Purpurbakterien
Schwefel- Grne Bakterien
The Sulfur Cycle Org. S
H2S
Assimilatorische Sulfatreduktion
Diss. S0 reduktion
S0
SO42-
Chap. 24.4 (Fig. 24.8)
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Sulfur Cycle
Hydrogen sulfide is a major volatile sulfur gas that is produced by bacteria via sulfate reduction or emitted from geochemical sources
Sulfide is toxic to many plants and animals and reacts with numerous metals
Sulfur-oxidizing chemolithotrophs can oxidize sulfide and elemental sulfur at oxic/anoxic interfaces
Chap. 24.4
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Catabolic Diversity
Fig. 4.22 Chap. 4.12
Fermentation Carbon flowOrganic compoundCarbon flow inrespirations Electron transport/generation of pmf
Aerobic respiration
Biosynthesis
Biosynthesis
BiosynthesisBiosynthesis
Organiccompound
Electronacceptors
Anaerobic respirationChemoorganotrophy
Chemolithotrophy
Phototrophy
Electron transport/generation of pmf
Anaerobic respiration
Electronacceptors
Aerobic respiration
LightPhotoheterotrophy Photoautotrophy
Electrontransport
Generation of pmfand reducing power
edonor
Chem
otro
phs
Phot
otro
phs
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Fermentation Carbon flowOrganic compoundCarbon flow inrespirations Electron transport/generation of pmf
Aerobic respiration
Biosynthesis
Electronacceptors
Anaerobic respirationChemoorganotrophy
Chem
otro
phs
Chemoorganotrophy
Anaerobic respiration, alternative electron acceptors (not O2) Energy generating process: Electron transport phosphorylation (and SLP) Catabolic end product: CO2 (exception: methanogenesis -> CH4) Example: Escherichia coli with nitrate
Aerobic respiration, O2 as electron acceptor Energy generating process: Electron transport phosphorylation (and SLP) Catabolic end product: CO2 Example 1: Paracoccus Example 2: Escherichia coli
Fermentation, anaerobic process without external electron acceptors Energy generating process: Substrate-level-phosphorylation (SLP) Example: Lactic acid fermentation Catabolic end product: lactic acid (homofermentative)
Chemoorganotrophy Energy and carbon source: organic compound(s)
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Chemolithotrophy
Energy source: reduced inorganic compound Electron acceptor, mostly O2 Energy generating process: Electron transport phosphorylation Catabolic end product: oxidized inorganic compound Example: Nitrification of Nitro(so)bacteria Carbon source: CO2 (in most bacteria/archaea)
Biosynthesis Electron transport/ generation of pmf
Anaerobic respiration
Electron acceptors
Aerobic respiration
-
Copyright 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Phototrophy
Energy source: Light Energy generating process: Electron transport phosphorylation Carbon source: CO2 (in most bacteria)
Biosynthesis Biosynthesis
Organic compound
Light Photoheterotrophy Photoautotrophy
Electron transport
Generation of pmf and reducing power
e donor