Post on 18-Dec-2015
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Photosynthesis in Microorganisms
General, Archaen, Anoxygenic, and Oxygenic
General Photosynthesis
Types of Phototrophs – based on Carbon source for synthesis
Fundamentals of Photsynthetic Activity and Cell Arrangement
• Highly folded inner membrane
• Thylakoid, lamelle, tubes, vessicles, chlorosomes, grana
• Pigments
• Chlorophyll, bacteriochlorophyll, rhodopsin, carotenoid, phycobillins
• Light reactions• electron transport, proton gradient,
ATPase
Fundamentals of Photsynthetic Activity and Cell Arrangement
• Internal Space
• Stroma, cytoplasm, carboxysome
• CO2-Fixation
• Calvin-Bensen Cycle, Reductive TCA cycle, glyoxylate pathway
• Dark Reactions
Modes or Styles of Photosynthesis
Archaean Unique, simple
Anoxygenic Various pigments: purple or
green H2S or H2 as electron donor
Oxygenic Similar to plants and algae H2O as electron donor
Reducing Power?
Cyanobacteria, Algae, Plants
Electrons from H2O reduce NADP+ to NADPH
NADPH used in reduction of CO2 to Glucose
Reducing Power?
Purple and green bacteria
Electrons from H2S (or H2) reduce NADP+ to NADPH
NADPH used in reduction of CO2 to Glucose
PigmentsSmall differences in Chemical
structureProperties
MagnesiumPorphorynPhytol
Large differences in light absorbed
Archaean Photosynthesis
Halophilic Bacteria Salterns, sea-salt farms,
Dead Sea, Great Salt Lake
Archaean Photosynthesis
Halophilic Bacteria Salterns, sea-salt farms,
Dead Sea, Great Salt Lake
Bacteriorhodopsin Examples
Halobacterium
Anoxygenic Phototsynthesis
Ancient form of metabolism – predates oxygenic photosynthesis and aerobic respiration
Bacteria Designated by Pigments – Purple or Green Electron Donor – Sulfur or Non-sulfur
Cyclic Photophosphorylation
Winogradsky Column
Anoxygenic Photosynthetic Bacteria
Group Genera Light Reactions
Dark Reactions
Comments
Purple Non-Sulfur
RhodospirillumRhodobacterRhodopseudomonas
Bchl a, bRed carotenoids
H2, ethanol as e- donors(rare heterotroph)
N-fixation in some
Anoxygenic Photosynthetic Bacteria
Group Genera Light Reactions
Dark Reactions
Comments
Purple Sulfur
ChromatiumThiocapsaEctothiocapsa
Bchl a, bRed carotenoids
H2S, S e- donors
Internal and External Sulfur Granules
Anoxygenic Photosynthetic Bacteria
Group Genera Light Reactions Dark Reactions
Comments
Green Sulfur
Chlorobium Bchl c, d, eGreen carotenoids(chlorosome)
H2S as e- donor
May contain gas vesicles
Anoxygenic Photosynthetic Bacteria
Group Genera Light Reactions Dark Reactions
Comments
Green Non- Sulfur
Chloroflexus Bchl c, d, eGreen carotenoids(chlorosome)
H2 as e- donor
(rare heterotroph)
filamentous