photosynthetic Microorganisms

1. PHOTOSYNTHESIS
Presented To:
Dr.karthik,
Asst.Prof of Microbiology,
Sacred Heart College,
Tirupattur.
Presented By:
Jayapriya .R,
Dept.of Microbiology,
Sacred Heart College,
Tirupattur.

2. PHOTOSYNTHESIS
• The process by which light energy is trapped and converted to chemical energy is
called Photosynthesis.
• Microorganisms derive energy not only from the oxidation of inorganic and organic
compounds, but also from light energy, which they capture and use to synthesize ATP
and reduce power (e.g., NADPH).
• Essentially, photosynthesis is the conversion of light energy from the sun into chemical
energy. The chemical energy is then used to convert CO2 from the atmosphere to more
reduced carbon compounds, primarily sugars. This synthesis of sugars by using carbon
atoms from CO2 gas is also called Carbon fixation.
• In Prokaryotes, Photosynthesis takes place in the Plasma membrane.
• In Eukaryotes, Photosynthesis takes place in the Chloroplast.

3. DIVERSITY OF PHOTOSYNTHETIC MICROORGANISMS
 1) Eukaryotic organisms
a) Plants
b) Multicellular Algae (Green algae, Red algae and Brown algae)
c) Unicellular Protists (Euglenoids, Dinoflagellates and Diatoms)
 2) Prokaryotic organisms
a) Cyanobacteria
b) Green sulfur bacteria
c) Green non-sulfur bacteria
d) Halobacterium sp. (Archaea)
e) Purple sulfur bacteria
f) Purple non-sulfur bacteria
g) Prochloron sp.

4. PHOTOSYNTHETIC PIGMENTS
• Pigments are chemical compounds which reflect only certain
wavelengths of visible light. This makes them appear "colorful".
• Flowers, corals, and even animal skin contain pigments which
give them their colors.
1) Chlorophyll
• Green pigment
• Three types:
Chlorophyll – a,
Chlorophyll – b and
Chlorophyll – c.

5. • Chlorophyll – a absorbs light of wavelength 430 nm (blue) to 662 nm
(red). The Chlorophyll – a is present in Plant, Algae and Cyanobacteria.
• Chlorophyll – b absorbs light of wavelength 453 nm to 642 nm.
Chlorophyll – b is present only in Plants, Chloroxybacteria and Green
algae (Chlorophyta).
• Chlorophyll – c is present only in Diatoms (Bacillariophyta),
Dinoflagellates, Golden algae (Chrysophyta) and Brown algae
(Phaeophyta).
• Bacteriochlorophyll is a type of Chlorophyll present only in Bacteria.
They absorbs maximally between 800 and 925 nm.

6. CAROTENOIDS
• Carotenoids are usually red, orange, or yellow pigments, and include the familiar compound
carotene, which gives carrots their color.
• Carotenoids absorb light maximally between 460 nm and 550 nm.
• Completely hydrophobic (fat soluble) and exist in lipid membranes.
• Carotenoids are classified into 2 types.
They are
i)Carotenes and (ii) Xanthophylls.
• Carotenes are present in the entire photosynthetic microorganism. • Xanthophylls
(Fucoxanthin) are present only in Brown algae, Golden algae and Diatoms.

7. PHYCOBILINS OR PHYCOBILIPROTEINS
• Phycobilins are water-soluble pigments, and are therefore found in
the Cytoplasm, or in the Stroma of the chloroplast.
• They occur only in Cyanobacteria (Blue – Green Algae; contains
blue pigment Phycocyanin, maximum absorption at 620 nm to 640
nm) and Rhodophyta (Red Algae; contains red pigment
Phycoerythrin, maximum absorption at 550 nm).

8. ACCESSORY PIGMENTS
• Carotenoids and Phycobiliproteins are often called Accessory pigments because of their
role in photosynthesis.
• Carotenoids and Phycobiliproteins cannot transfer sunlight energy directly to the
photosynthetic pathway, but must pass their absorbed energy to chlorophyll. For this
reason, they are called Accessory pigments.
• One very visible Accessory pigment is Fucoxanthin (a type of Xanthophylls) the brown
pigment which colors kelps and other Brown algae, Golden algae as well as the Diatoms.
• Accessory pigments also protect microorganisms from intense sunlight, which could
oxidize and damage the photosynthetic apparatus.

9. PHOTOSYSNTHESIS REACTIONS
• Photosynthesis takes place in two stages.
• In the First stage, called the Light reactions, the light energy is used to convert ADP
and Phosphates to ATP. In addition, in the predominant form of the light-dependent
reactions, the electron carrier NADP+ is reduced to NADPH. The coenzyme NADPH,
like NADH, is an energy- rich carrier of electrons
. • In the Second stage, the light-independent (Dark) reactions, these electrons are used
along with energy from ATP to reduce CO2 to Carbohydrate sugar.