Cyanobacteria PDF

‫‪Cyanobacteria‬‬ ‫د‪ /‬إيمان عبدالرازق محمد‬  Cyanobacteria Classification: Super kingdom: prokaryota Kingdom: Monera Division: cyanophyta Cl...

‫‪Cyanobacteria‬‬ ‫د‪ /‬إيمان عبدالرازق محمد‬  Cyanobacteria Classification: Super kingdom: prokaryota Kingdom: Monera Division: cyanophyta Class: Cyanophyceae )Myxophyceae) 1- order: 2- order: 3- order: Chroococales Oscillatoriales Nostocales Genus: Gleocapsa Genus: Oscillatoria Genus: Nostoc ✓ Single cells or ✓ Filamentous ✓ Loosely cells bound ✓ Filamentous cyanobacteria cyanobacteria into gelatinous with heterocysts. irregular colonies.  General Characteristics of Cyanophyta Commonly known as Blue-green algae, Blue-green bacteria, Cyanobacteria. The simplest algae occurring essentially as solitary cells or be aggregated into plate–like or globular colonies. or occurring as filamentous form. Surrounded by thin mucilage layer Autotrophic (Photosynthetic). Contain chlorophyll (a). Lack chlorophyll (b). Contain accessory pigments: xanthophyll, carotenoid (B-carotene) and billi-protein (phycocyanean this pigment give unique blue-green color for this algal division). Chloroplast is absent (photosynthetic pigments are located in thylakoids, which lie free in the cytoplasm).  Cyanophyta store their food as unique starch compound named as cyanophycean starch. Cyanophyta lacking flagellated stage (algae that related to this division are motile by gliding movement or regulate the buoyancy through water column by gas vacuoles. Sexual reproduction is absent. Produce asexually (endospores, akinate), and vegetative (binary fission, fragmentation, hormogonia). The structural part of cell wall consists of peptidoglycan, the cell are embedded in sheath of mucilage which are often lighter than water and therefore help keep the algae up near the surface of the water. They live in aquatic environments including oceans, ponds, lakes, tidal flats, and moist soil.  Cell Structure The cell structure is very primitive. Each cell is composed of two parts: Cell wall a) cell wall Chromoplast b) protoplast. Central body The cell wall is composed of 2 layers: The inner layer of which is thin and firm composed of peptidoglycan. The outer layer of the wall is thicker and gelatinous known as the sheath and mainly constituted of pectic compounds. The protoplast consists of 2 parts: peripheral pigmented (coloured) region surrounding a colourless central region. It contains the blue pigment phycocyanin together with chlorophyll Cell wall and known as chromoplasm. Chromoplast Central body The colourless inner region (central body) contains several chromatin granules (DNA) which represent a primitive type of nucleus that lacks nuclear membrane and nucleoli. Cyanobacterial cell Forms of Cyanobacteria 1 Unicellular 2 Colonial Multicellular 3 (filamentous forms)  Forms of Cyanobacteria 1. Unicellular or aggregate e.g. Gloeocapsa sp 2. Colony MicrocystisLab.jpg (147108 bytes) e.g. Microcystis sp  3. Filamentous forms a) Unbranched e.g. Nostoc sp b) Branched e.g. Stigonema sp  Reproduction 1. Vegetative reproduction. 2. Asexual reproduction. Binary fission By Akinetes Fragmentation By Endospores Hormogonia  1- Vegetative reproduction. Binary fission: A cell divides into two in roughly equal halves. Nucleus divides mitotically first and then the cytoplasm. Each grows to original form. This is the most common type. (A constriction is formed in the middle of the cell) (Extends from the surface inwards towards the center) (Division into two cells) Fragmentation Filament breaks into fragments. Each fragment gives rise to a new filament. Usually fragmentation occurs at the Heterocysts This fragment is capable of creeping movements in the gelatinous sheath until it escapes and grows into a new filament. Hormogonia: Trichomes break up within the sheath into short segments called hormogonia or hormogones. Each segment grow into a new filament (e.g. in Nostoc and Oscillatoria). Nostoc Oscillatoria  2. Asexual reproduction By Akinetes (Rest spore) AkineteHeterocystLMHigh300Lab.jpg (15127 bytes) Vegetative cells (found close to heterocysts) Enlarge in size Become rich in food materials and form a thick wall These akinetes are yellow or brown in colour and they are very resistant to un-favourable conditions When the conditions are favourable The akinetes germinate into new filaments. By Endospores Formed by coccoid (spherical) cyanobacteria. The protoplasm divides several times in different planes without growth between successive divisions. Smaller than the original cell. Similar to bacterial endospores. Release through an apical pore after secreting a wall around it and enlarge to mature organisms.  Importance of Cyanobacteria Nitrogen fixation: are able to fix nitrogen gas into ammonia (NH3), nitrites (NO−2) or nitrates (NO−3) which can be absorbed by plants and converted to protein and nucleic acids. Can be used as food (Japan, Chad, and China) Cyanophyta Toxin: Cyanobacteria can produce neurotoxins, cytotoxins, endotoxins and hepatotoxins and are called cyanotoxins. ✓ Can pollute the water source (Lake). ✓ High concentration may cause fish toxicity and other microorganism.