Blue-green algae, or cyanobacteria, are photosynthetic prokaryotes that evolved from endosymbiotic bacteria. They contain chlorophyll and accessory pigments that allow them to perform oxygenic photosynthesis using two photosystems. This generates ATP through cyclic and non-cyclic photophosphorylation. Cyanobacteria have diverse applications including nitrogen fixation in agriculture, production of anti-inflammatory and anti-microbial compounds, and use as a nutritional supplement.

1. Energy from visible radiation-
Blue Green Algae
Presented by
JERIMON P J
1st MSc Microbiology
Department of Microbial Biotechnology
Bharathiar University

2. Synopsis:
 What is Blue Green Algae?
 Evolution
 Classification
 Pigments in Blue Green Algae
 Energy production in Blue Green Algae
 Applications of Blue Green Algae

3. What is Blue Green Algae?
• Blue-green algae are commonly known as
Cyanobacteria, which belongs to a large
group of prokaryotes and mainly
photosynthetic organisms.
• The term cyanobacteria is derived from the
Greek word, meaning “blue” and bacteria.
• Cyanobacteria is a group or phylum
consists of photosynthetic bacteria that
mostly live in aquatic and moist soil
habitats.

4. Evolution of Cyanobacteria:
• As per endosymbiotic theory, the higher organism
(eukaryotes) which have the ability to produce their own
food are evolved from the prokaryotes that is ingested
with a primitive photosynthetic prokaryotic organism
known as, cyanobacteria.
• This endosymbiotic event led to the evolution of the
three primary endosymbiotic higher organisms like
green plants, red algae, and glaucophytes.
• Later, these three groups make up the monophyletic
group known as Archaeplastida. The primitive
endosymbiotic prokaryote that is cyanobacterial cell
which was present inside the eukaryote is theorized to
have evolved to become the chloroplast (plastid).
• The chloroplast and the cyanobacterial cell seems to
have similar features, either by morphologically, or
genetically or biochemically.
• Later on, following the primary endosymbiosis,
secondary and tertiary endosymbiotic evolution took
place, and these are believed to have led to later lineages
of photosynthetic eukaryotes that are capable of
synthesizing their own food.

5. Classification:
• In Whittaker’s five-kingdom classification, Cyanobacteria is placed in the
phylum called Cyanophyta which is one of the phylum in Kingdom Protista.
But, these organisms do not possess true roots, stems, and leaves as higher
plants.
• At present, Cyanophyta (also called blue-green algae) is now referred to
Cyanobacteria, is placed in the phylum of Bacteria. This is due to these
organisms are single celled or prokaryotic in nature. Thus, they are now
classified as bacteria belonging to Phylum Cyanobacteria.
• Cyanobacterial sub-groups are classified based on morphology are listed
below.
Chroococcales
Pleurocapsales
Oscillatoriales
Nostocales
Stigonematales

6. Chroococcales:
• Chroococcales are the organisms that are found in colonies
of two, four, or eight cells with a transparent protective
covering sheath with photosynthetic pigments. They mostly
prefer fresh water so always found in sludge of lakes and
river bottoms.
• Examples: Chroococcus disperses, Chroococcus
submarinus.
Pleurocapsales:
• Pleurocapsales are spore forming and nitrogen fixing
cyanobacteria, which are mainly found in the marine
environments. Members of this group are very difficult to
culture in laboratory as pure cultures.
• Examples: Pleurocapsa minor, Pleurocapsa species.

7. Oscillatoriales:
• They always survive in freshwater environments and
also in hot springs. These are unbranched filamentous
algal cells which are motile and moves like slow
rhythmic oscillating motion. Thus these organisms are
named as Oscillatoriales.
• They reproduce mainly by the process of
fragmentation, where each filaments are broken into
fragments known as hormogonia. They live in fresh
water ponds and uses photosynthesis to survive and
reproduce.
• Examples: Oscillatoria fischeri, Oscillatoria indica,
Oscillatoria sancta, Oscillatoria amoena.

8. Nostocales:
• These organisms are filamentous both in simple and branched
forms. They occur in single strands or multiple strands within a
sheath. The vegetative cells of this order are divided into
heterocysts which has a thick hyaline protoplast. They are
involved in nitrogen fixation as well as akinetes that have in
place thick cell walls that allow them to survive when
conditions are unfavourable.
• Examples: Nostoc azollae, Nostoc comminutum, Nostoc
thermotolerans
Stigonematales:
• They have similar traits to those of Nostocales. Both the two
group of organisms have similar characteristics. These also
include traits known as trichomes with heterogeneous cellular
composition and as well as heterocysts and akinetes vegetative
cells. Some of the other traits associated with the order
Stigonematales includes multiseriated filaments with true
branching.
• Examples: Stigonema species, Fischerella species,
Hapalosiphon species.

9. Pigments in cyanobacteria:
• Cyanobacteria are blue greenish color due to the presence of some
pigments in the cell.
• Photosynthetic pigments are light harvesting molecules found in the
thylakoid membranes. They capture the light energy that are necessary
for photosynthesis. The pigments involved in photosynthesis are listed
below.
• Primary Pigment- Chlorophyll a
• Accessory pigment- Chlorophyll b, Chlorophyll c, Chlorophyll d,
carotenoids
• Phycobilins- phycoerythrin, phycocyanin
• Combination of both Phycobilins and Chlorophyll makes the
organism to appear blue green in color and hence it is termed as Blue
Green Algae

10. Chlorophyll:
• Chlorophylls are Magnesium porphyrin derivative.
• It is the primary pigment and forms the reaction centre of
photosystems.
• Chlorophylls absorbs maximally at red and blue region and
reflects green light.
• The molecule consists of a hydrophobic purrole head and
hydrophilic phytol tail with a central magnesium atom.
Phycobillins:
• Phycobillins are water soluble proteins which contain covalently
bound linear tetra pyrroles (bilins) as chromophores present
inside the granules.
• They occur on the outer surface of the thylakoid of cyanobacteria.
• Phycobiliproteins are red or blue in colour, contains tetrapyrroles
coupled to proteins. Some of the phycobiliproteins are
Phycocyanin and Phycoerythrin.
• These proteins form a structure called phycobilisomes which are
attached to photosynthetic pigments.

11. Energy Production in Cyanobacteria:
Photosynthesis
• Photosynthesis is the process of conversion of light energy into
chemical energy mainly by plants and certain organisms. The general
equation of photosynthesis is
6CO2 + 6H2O → C6H12O6 + 6O2
• Two types of photosynthesis oxygenic photosynthesis and anoxygenic
photosynthesis.
• In oxygenic photosynthesis, H2O is split and supplies the electron to
the reaction center. Because oxygen is generated as a byproduct and is
released, this type of photosynthesis is referred to as oxygenic
photosynthesis.
• In anoxygenic photosynthesis, the reduced compounds serve as the
electron donor. Thus, oxygen is not generated; this type of
photosynthesis are called anoxygenic photosynthesis.

14. Mechanism of energy production in cyanobacteria:
• Oxygenic photosynthesis is used by cyanobacteria, algae, and plants.
• Cyanobacteria contain chlorophyll while other forms of bacteria contain
bacteriochlorophyll.
• The chlorophyll in PSI is called P700, and the chlorophyll in PSII is called
P680, for the wavelengths of light each absorbs most efficiently.
• Electron flow happens through two different electron transport chains that
are connected; together, these electron transport chains are called the Z
scheme.
• The compounds used to carry electrons include pheophytin (chlorophyll
without the magnesium ion (Mg2+) center), quinones, cytochromes,
plastocyanins (copper-containing proteins), nonheme iron sulfur proteins,
ferredoxin, and flavoproteins.

15. • In cyanobacteria and in all phototrophic
eukaryotes, there are two distinct,
interconnected photosystems:
photosystem I and photosystem II.
• Photosystem I absorbs longer wavelength
of light and funnels its energy to a special
reaction centre chlorophyll ‘a’ molecule
called P700.
• The P700 signifies that this reaction centre
chlorophyll ‘a’ absorbs light at a
wavelength of 700 nm most effectively.
• Photosystem II absorbs light at shorter
wavelengths and transfer its energy to the
reaction centre chlorophyll molecules
called P680.

16. Cyclic Photophosphorylation:
• When the PS I antenna chlorophylls funnel light energy to the reaction
centre chlorophyll P700, the latter gets excited and its reduction potential
becomes very negative. The excited or high-energy electron of P700 is
captured by a special chlorophyll ‘a’ molecule (A) or an iron sulphur protein
(FeS).
• The electron is eventually transferred to ferredoxin. The latter transfers
electron to a cyclic route through a series of electron carriers (cytochrome
b563 → plastaquinone → cytochrome b6 → cytochrome f → plastocyanin)
back to oxidized P700.
• Since the electrons travel in a cyclic pathway (i.e. they originate from P700
and come back to the P700), the process is called cyclic
photophosphorylation in which only PS I is involved.
• During cyclic phosphorylation, ATP is generated in the region of
cytochrome b6.

17. Non-Cyclic Photophosphorylation:
• In this process, both PS I and II are involved. The reduction potential of P680
chlorophyll ‘a’ molecule of PS II is very electropositive, slightly more positive
than that of the H2O/O2 couple.
• This facilitates the first step in oxygenic electron flow, the splitting of water
(photolysis) into oxygen and hydrogen ions (2H+).
• Photolysis donates an electron to atoms the oxidized P680 molecule following
the absorption of a quantum of light near 680 nm.
• The P680 molecule is now excited and reduces pheophytin ‘a’ which is
chlorophyll ‘a’ without the magnesium atom.
• Electrons subsequently travel through quinone, plastaquinone, cytochrome b6
(ATP is generated in the region of cytochrome b6), cytochrome f and
plastocyanin; the latter donates electrons to photosystem I.
• The electron is accepted by the oxidized reaction centre chlorophyll ‘a’ of PS I
(P700) which has previously absorbed light quanta and begun the steps to lead
the reduction of NADP+ into NADPH.

18. Cyclic photophosphorylation
Non-Cyclic photophosphorylation

19. Applications of cyanobacteria:
• Cyanobacteria may possess the ability to produce substances that could one day serve as
anti-inflammatory agents and combat bacterial infections in humans
• Cyanobacteria can be helpful in agriculture as they have the capability to fix
atmospheric nitrogen to soil.
• They have symbiotic relationship with protozoa, fungi, and nitrogen fixing species form
associations with angiosperms. They are photosynthetic partner in most of lichen
association. Eg., Anabaena azollae colonizes the floating water fern
• CYANOVIN, a secondary metabolite has been shown to possess anti-HIV activity.
• Consumption of edible blue green algae may also reduce risks of cataracts and age
related macular degeneration.
• Sulfate polysaccharides exhibit antitumor, anticoagulant, anti-mutagenic,
antiinflammatory, antimicrobial, and even antiviral activity against HIV, herpes, and
hepatitis.
• It serves as a "complete whole food" which contains 60% protein with all essential
amino acids in perfect balance.

20. THANK YOU