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

ChlorophyllCarotenoids

http://wfc3.gsfc.nasa.gov/MARCONI/images-basic/spectrum.jpg

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