Cyanobacteria and Salient Features of it

Cynobacteria and its characterstics features

1. GREEN BACTERIA , PURPLE BACTERIA AND CYANOBACTERIA Guided by - Dr. Kamlesh Shukla Semester - I

2. INTRODUCTION Photosynthesis is the biological process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose or other sugars. This process involves the utilization of sunlight, carbon dioxide, and water to produce glucose and oxygen. There are two main types of photosynthesis: oxygenic photosynthesis and anoxygenic photosynthesis. Oxygenic Photosynthesis : Photosynthesis takes place in presence of oxygen. 6CO 2 + 6H 2 O + Light energy  C 6 H 12 O 6 + 6O 2 Anoxygenic Photosynthesis : Photosynthesis take place in absence of oxygen. CO 2 + 2H 2 S + Light energy  (CH 2 O) + 2S + H 2 O

3. CLASSIFICATION Photosynthetic bacteria Oxygenic Anoxygenic Cyanobacteria e.g : Nostoc Oscillatoria Use H 2 O as electron donor Uses H 2 S as electron donor Organic electron donors PSB e.g : Allochromatium GSB e.g : Chlorobiota GNSB e.g : Chloroflexus PNSB Rhodospirillum

4. CYANOBACTERIA Cyanobacteria, also known as blue-green algae, are a group of photosynthetic bacteria that are capable of producing oxygen through photosynthesis . Photosynthesis: Cyanobacteria are autotrophic organisms, meaning they can produce their own food through photosynthesis. They use chlorophyll for photosynthesis, similar to plants, and are responsible for a significant portion of the Earth's oxygen production. Pigments: In addition to chlorophyll, cyanobacteria contain other pigments such as phycocyanin and phycoerythrin , which give them their characteristic blue-green color. These pigments are involved in capturing light energy for photosynthesis . Habitats: Cyanobacteria are found in a wide range of environments, including freshwater, marine environments, and terrestrial habitats. They can thrive in diverse conditions, from hot springs to polar regions, and they are often found in symbiotic relationships with plants, fungi, and lichens.

5. PURPLE BACTERIA Purple bacteria are a group of photosynthetic bacteria that belong to the phylum Proteobacteria . They are anoxygenic photosynthesizers , meaning they do not produce oxygen as a byproduct during photosynthesis. Instead, they use alternative electron donors and acceptors in their photosynthetic pathways. Purple bacteria are further categorized into two main groups based on their photosynthetic pigments and the way they capture light energy: the purple sulfur bacteria the purple non-sulfur bacteria.

6. PURPLE SULPHUR BACTERIA Purple sulfur bacteria are a group of photosynthetic bacteria that belong to the class Gammaproteobacteria . They are characterized by their ability to carry out anoxygenic photosynthesis, a process that does not produce oxygen as a byproduct. Instead, these bacteria use sulfur compounds as electron donors during photosynthesis . Photosynthetic Pigments: Purple sulfur bacteria contain bacteriochlorophylls a & b, which are pigments that capture light energy during photosynthesis. The combination of these pigments, along with carotenoids, gives these bacteria their characteristic purple or red color. Metabolism: They are obligate anaerobes i.e can only carry out photosynthesis in the absence of oxygen. They use reduced sulfur compounds, such as hydrogen sulfide ( H 2 ​ S ), as electron donors. Habitats: Purple sulfur bacteria are commonly found in aquatic environments, such as stagnant water bodies, mud, or sediments where hydrogen sulfide is available. They thrive in environments with low oxygen levels.

7. PURPLE NON-SULPHUR BACTERIA Purple non-sulfur bacteria are a group of photosynthetic bacteria that belong to the phylum Proteobacteria . As the name suggests, these bacteria do not rely on sulfur compounds as electron donors in their photosynthetic process, distinguishing them from purple sulfur bacteria, which use reduced sulfur compounds . Pigments: Purple non-sulfur bacteria contain bacteriochlorophyll pigments, similar to other photosynthetic bacteria. These pigments absorb light energy for photosynthesis. In addition to bacteriochlorophyll , they may also have other accessory pigments such as carotenoids . Metabolic Flexibility: Purple non-sulfur bacteria are metabolically versatile. They can switch between different metabolic modes depending on the availability of light and organic substrates. In the absence of light, they can switch to using organic compounds as energy sources through chemotrophic metabolism. Photosynthetic Process: Purple non-sulfur bacteria perform anoxygenic photosynthesis, which means they do not produce oxygen as a byproduct. Instead of using water as an electron donor, they utilize alternative sources like organic compounds or hydrogen . Habitat: These bacteria are often found in environments rich in organic matter, such as sediments, decaying plant material, and other environments where organic compounds are abundant. They are also commonly present in anaerobic environments.

8. GREEN BACTERIA The term "green bacteria" is broad and can refer to various groups of bacteria that share the common feature of containing pigments, such as chlorophylls, that give them a green color. The two main types of green bacteria are: G reen sulfur bacteria G reen non-sulfur bacteria . Both belong to the phylum Chlorobi , and they are known for their ability to carry out anoxygenic photosynthesis.

9. GREEN SULPHUR BACTERIA Green sulfur bacteria are a group of photosynthetic bacteria that belong to the phylum Chlorobi . Like other photosynthetic bacteria, they are capable of harnessing light energy for photosynthesis, but they have specific characteristics that distinguish them . Photosynthetic Pigments: Green sulfur bacteria contain unique photosynthetic pigments called chlorobins , including chlorosome -associated bacteriochlorophylls . These pigments, such as bacteriochlorophylls c, d, or e , give these bacteria their characteristic green color. Metabolism: Green sulfur bacteria are anoxygenic phototrophs , meaning they carry out photosynthesis without producing oxygen as a byproduct. They use reduced sulfur compounds, such as hydrogen sulfide ( H 2 ​ S ), as electron donors during photosynthesis. Habitats: Green sulfur bacteria are often found in anoxic (oxygen-depleted) environments such as the bottom layers of stratified water bodies, sediments, and other environments where hydrogen sulfide is present. They can thrive in conditions with limited or no oxygen.

10. GREEN NON-SULPHUR BACTERIA Green non-sulfur bacteria are a group of photosynthetic bacteria that do not rely on sulfur compounds for their photosynthetic process. They are anaerobic or facultatively anaerobic, meaning they can perform photosynthesis in the absence of oxygen or in low-oxygen environments. These bacteria typically inhabit environments where oxygen is limited . Pigments: Like green sulfur bacteria, green non-sulfur bacteria contain bacteriochlorophyll pigments, which play a role in capturing light energy for photosynthesis. However, they may also have additional pigments such as carotenoids . Metabolism: Green non-sulfur bacteria are versatile in their metabolism. They can switch between phototrophic (photosynthetic) and chemotrophic (using organic or inorganic compounds as an energy source) modes depending on the availability of light and nutrients . Habitat: These bacteria are often found in anaerobic environments, such as sediments, mud, and the bottom of stagnant water bodies. They can also be associated with organic-rich environments.