Cyanobacteria are photosynthetic group of bacteria that can fix atmospheric nitrogen essential for aminoacid biosynthesis. Earlier they were called as blue green algae. Now that name is not used because they are not belongs to the algae.
Basic Civil Engineering first year Notes- Chapter 4 Building.pptx
Mks cyanobacteria
1. Cyano bacteria Dr. M.K. SATEESH Molecular Diagnostics Laboratory Department of Microbiology and Biotechnology Bangalore University, Jnana Bharathi campus Bangalore-560 056 Microcystis Gleocapsa Nostoc Anabaena Scytonema Spirulina
2. 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Billion Years Before Present Earth formed Precambrian Time: The Time of Prokaryotes Phanerozoic Time Eukaryotic Time Archaean Era: Era of Archaea Proterozoic Era: Era of Cyanobacteria First Life First Cyanobacteria O 2 First Eukaryotes Timeline of Planet Earth
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4. Cyanobacteria terminology - Division Cyanophyta - Cyanobacteria ‘formerly known as’ Blue Green Algae - Cyano = blue - Bacteria – acknowledges that they are more closely related to prokaryotic bacteria than eukaryotic algae
5. Bacteria Archeae Other Eukaryotes Animalia Fungi Green Plants Red Algae Prokaryotes Eukaryotes
23. Features Trichome – row of cells Mucilaginous sheath – layer of mucilage outside of the cell wall. } Filament
24. Features Mucilaginous Sheath – Function – protects cells from drying and involved in gliding. Sheath is often colored: Red = acidic Blue = basic Yellow/Brown = high salt
25. Features Heterocyst – thick walled cell, hollow looking. Larger than vegetative cells. FUNCTION – provides the anerobic environment for N fixation. H- heterocyst
43. Cyanobacterial fission Gloeocapsa sp., algae. (Light micrograph of Gloeocapsa sp., a type of blue-green algae or cyanobacteria. They reproduce solely by fission, a form of asexual division in which two identical algae are produced. Binary fission of cyanobacteria Binary fission
58. Schematic summary figure of the cyanobacteria life cycle (prototype for species of the order Nostocales). Vegetative cells grow only until nitrogen depletion forces them to build heterocysts, thus enabling the cells to grow further by nitrogen fixation. At the end of summer vanishing light prevents further growth; some of the cells differentiate into akinetes, the resting spores which sink to the bottom where they take up nutrients and mature during winter and spring. Finally, if the conditions are sufficiently favourable the cells germinate and begin to rise to the surface with the help of gas vacuoles. Here, light is abundant and growth of vegetative cells takes place, starting the life cycle again.
61. Microcystis aeruginosa is a unicellular, planktonic freshwater cyanobacterium. The existence of intracellular structures, the gas vesicles, provides cells with buoyancy. These hollow, gas-filled structures can keep Microcystis cells close to the surface of water body, where there is optimal light and oxygen for growth. Thus, when the water column is stable, the colonies can accumulate at the water surface and form surface water blooms. Cells range from 2.61 to 5.40μm in diameter, and can be either ovoid or spherical in shape. The extracellular covering of cell was divided into several layers: the cytoplasmic membrane or plasmalemma, the peptidoglycan layer, and the multilayered structure of the cell wall. Microcystis is light dependent and oxygenic, but cells may live under the dark anaerobic conditions for periods of time in eutrophic lakes. Microcystis aeruginosa often form blooms in eutrophic lakes and reservoirs. Surface water blooms can cause anaerobic conditions below the surface in the water and thus make other phytoplankton including M. aeruginosa themselves live in an unfavorable environment. However, M. aeruginosa appeared to be more tolerant to dark anaerobic conditions, which may be important to the dominance of M. aeruginosa in eutrophic lakes.
62. Gloeocapsa may be unicellular or made up of small groups of cells grouped within concentric mucilage envelopes. The individual colonies are usually spherical, microscopic, and enclosed within larger masses of mucilage. The cells are oval-shaped or ellipsoidal, and hemispherical after dividing. Each cell has a rounded, firm, inner mucilaginous sheath surrounded by older sheath material from the parent cell, revealing the pattern of cell division. The sheaths are colorless or vivid shades of yellow, brown, red, orange, blue, or violet, and may be affected by changes in pH. The cells are usually bright blue-green or olive green and do not have distinct gas vesicles. Inner mucilage sheaths surrounds each cell or recently divided pairs of cells, as indicated. Staining the specimens with India Ink makes the mucilage clearly visible against the dark background. From Greek gloia , "glue" + Latin capsa , "box"
63. Spirulina are Gram-negative, with soft cell walls that consist of complex sugars and protien. They are undifferentiated and filamentous. Spirulina can be rod- or disk-shaped. Their main photosynthetic pigment is phycocyanin, which is blue in color. These bacteria also contain chlorophyll a and carotenoids. Some contain the pigment phycoythrin, giving the bacteria a red or pink color. Spirulina also have gas vesicles, giving them bouyancy in the aquatic environments they inhabit. Spirulina are photosynthetic, and therefore autotrophic. Spirulina reproduce by binary fission.
64. Nostoc is a diverse genus of cyanobacteria. They are found in gelatinous colonies, composed of filaments called "trichomes" surrounded by a thin sheath. They are common in both aquatic and terrestrial habitats. These organisms are known for their unusual ability to lie dormant for long periods of time and abruptly recover metabolic activity when rehydrated with liquid water. The bacteria's ability to withstand freezing and thawing cycles make them well-adapted to living in extreme environments, such as the Arctic and Antarctica. They can fix atmospheric nitrogen, making them good candidates for environments with low nitrogen rates. Nostoc , first discovered in the 19th century, is one of the most widespread phototrophic bacteria in the world. As a nitrogen fixer, these bacteria may provide plants with important nutrients and therefore can be used agriculturally. In 1988 a terrestrial species, Nostoc commune , was found to harbor a previously unidentified UV-A/B absorbing pigment. This protective pigment has enabled them to survive not only while under hydration-related stress, but in areas of extreme UV radiation as well.
66. Anabaena are heterocyst-forming, photoautotrophic cyanobacteria that perform oxygenic photosynthesis. Anabaena grow in long filaments of vegetative cells. During times of low environmental nitrogen, about one cell out of every ten will differentiate into a heterocyst. Heterocysts then supply neighboring cells with fixed nitrogen in return for the products of photosynthesis, that they can no longer perform. This separation of functions is essential because the nitrogen fixing enzyme in heterocysts, nitrogenase, is unstable in the presence of oxygen. Due to the necessity of keeping nitrogenase isolated from oxygen, heterocysts have developed elements to maintain a low level of oxygen within the cell. To prevent the entrance of oxygen into the cell, the developing heterocyst builds three additional layers outside the cell wall, giving it its characteristic enlarged and rounded appearance, thus the rate of oxygen diffusion into heterocysts is 100 times lower than of vegetative cells. One layer creates an envelope polysaccharide layer where the nitrogen is fixed in a oxygen-restricted milieu. To lower the amount of oxygen within the cell, the presence of photosystem II is eliminated, and the rate of respiration is stepped up to use up excess oxygen.
67. Scytonema is a filamentous aquatic bacterium and can be found in fresh water environments. S. crispum is important ecologically because it has the ability to fix nitrogen from the environment. Because of this, scytonema can also form symbiotic relationships with other organisms such as fungi. The genus Scytonema is especially important because these bacterium have been found to produce special chemicals such as toxins. In 2003 an anti-HIV protein, scytovirin, was isolated from a bacterial species of Scytonema . Scytonema reproduce by hormogonia, which develop at the ends of branches and bud from sheaths. Hormogonia germinate at both ends and form isopolar filaments. Scytonema crispum fixes nitrogen, thus providing nitrogen to the leaves of plants on which it is growing. This allows for some symbiotic relationships to be established with other organisms. Within scytonema's filamentous cells are heterocysts which are structures without oxygen that allow the enzyme nitrogenase to fix atmospheric nitrogen into ammonium.
