Dr MAQSOOD AHMED MOHAMMED Lecturer In Microbiology S
Dr. MAQSOOD AHMED MOHAMMED Lecturer In Microbiology S. K. R. Govt. Degree College. Gudur, SPSR Nellore
• CYANOBACTERIA
• Cynobacteria also known as Cyanophyta • a phylum of bacteria that obtain their energy through photosynthesis • the only photosynthetic prokaryotes able to produce oxygen • The name "cyanobacteria" comes from the color of the bacteria • Greek: κυανός (kyanós) = blue
What are cyanobacteria? • Cyanobacteria are sometimes considered algae, but they are actually bacteria (prokaryotic) • where the term "algae" is now reserved for eukaryotic organisms. • They also derive their energy through photosynthesis, but lack a nucleus or membrane bound organelles, like chloroplasts. •
• Cyanobacteria used to be called blue-green algae but they are prokaryotes • By producing oxygen as a byproduct of photosynthesis, cyanobacteria are thought to have converted the early oxygen-poor, reducing atmosphere, into an oxidizing one, causing the "rusting of the Earth”
• Actually, cyanobacteria may have evolved into the first chloroplasts, as evidenced by similar structural and genetic traits. • Cyanobacteria have a unique set of pigments used in photosynthesis, called the phycobiliproteins (phycobilins), which can give some of them a bluegreen color. cyanotoxins
• Cyanobacteria are also responsible for many of the Harmful Algal Blooms (HABs) that cause ecological, economical and public health concerns in waterways, many times through the production of cyanotoxins
Cyanobacteria: distribution and numbers • Include ca. 200 genera and 2000 species • All kinds of environments i. e. “ubiquitous”, mostly aquatic (rarely at p. H< 4 -5), • Terrestrial on rocks and soils, deserts, polar regions, other extreme habitats as thermal pools (ca. 70 °C), hypersaline waters etc.
Cyanobacteria: Traditional taxonomic classification in orders 1. Order Chroococcales 2. Order Oscillatoriales 3. Order Nostocales Unicells, as individual cells orcolonies. Spores may occur, never akinetes or heterocysts Uniseriate trichomes, never akinetes or heterocysts unbranched or falsebraching Uniseriate trichomes, with akinetes and heterocysts. Unbranched or falsebraching 4. Order Stigonematales Uni- or multiseriate trichomes, with akinetes and heterocysts. True branching
Why treat cyanobacteria together with the algae? 1. Oxygenic photosynthesis and pigments (chlorophyll a) as in algae and plants light CO 2 +2 H 2 O chlorophyll a (CH 2 O) + O 2 +H 2 O All other photosynthetic bacteria (e. g. green sulfurbacteria) have bacterial chlorophyll and anoxic photosynthesis CO 2 +2 H 2 S light (CH 2 O) + 2 S + H 2 O Bacterial chlorophyll
2. Cyanobacteria (blue greens) occur with algae in similar habitats, mainly aquatic environments. Similar ecological function (as primary producers). Together with the algae they stand for ca. 40 % of global primary production
Cyanobacteria: evolutionary history • Oldest photosynthetic organisms, oldest fossil records ca. 3500 million years • Dominant form of life on Earth 1500 - 600 million years before present (BP) (e. g stromatolites) • Photosynthesis resulted in a gradual increase of O 2 in the atmosphere • Primary endosymbiosis lead to algal chloroplasts • ca. 1600 million years ago
3. Algal (and plant) chloroplasts originated from primary endosymbiosis between heterotrophic eukaryote and a free living cyanobacterium Cyanobacterium taken up by phagotrophic eukaryote and eventually transformed into a chloroplast nucleus chloroplast cyanobacterium
Cyanobacteria: General Characteristics As all Prokaryotes absence of organelles: • Nucleus • Chloroplasts • Mitochondria • Golgi bodies (dictyosomes) • Endoplasmatic reticulum (ER)
Pigments: chlorophyll a (three genera with chlorophyll a + b) phycobilins phycoerythrin phycocyanin allophycocyanin carotenoids A variety, some are specific, others as in algae and plants scytonemin - extra cellular, UV-shielding pigment
Storage products: • Cyanophycean-starch ( -1, 4 glucan) • Cyanophycin-grains: N-reserve, a co-polymer of two amino acids (asparagine and arginine) • Volutin grains - polyphosphate granules • Lipids
Cyanobacteria: systematic characters Morphology Unicellular as colonies (Order Chroococcales) single cells attached (cells polar) free living
Cyanobacteria: systematic characters Morphology Multicellular (filamentous) uniseriate trichome multiseriate trichome
Cyanobacteria: systematic characters False branching
Cyanobacteria: systematic characters True branching only in some representatives of the order Stigonematales
Orde Stigonematales no marine representatives Stigonema
Vegetative reproduction: by binary division and fragmentation
Vegetative reproduction: by hormogonia, only in some filamentous forms Oscillatoria hormogonium “separation discs” (necridia) Lyngbya
Vegetative reproduction: Akinetes: resting cells with thick cell walls and enriched with storage products Anabaena Akinetes may survive for years in darkness and under dry conditions
Asexual reproduction: Formation of spores, only in some unicellular forms endospores Dermocarpa exospores Chamaesiphon
Sexual reproduction by gametes: completely absent
Cyanobacteria: systematic characters Heterocytes (heterocysts) are cells with nitrogen fixation as a special function. Heterocytes only present in some filamentous forms (Nostocales, Stigonematales), though N-fixation may occur also in some non- heterocysteous forms N 2 nitrogenase NH 4+ intercalary heterocyst terminal heterocyst akinete
Biotechnological applications • Cyanobacteria has potential to generation of renewable energy by converting sunlight into electricity • Cyanobacteria may possess the ability to produce substances that could one day serve as anti-inflammatory agents and combat bacterial infections in humans • Spirulina's extracted blue color is used as a natural food coloring in gum and candy • Some cyanobacteria are sold as food, notably Aphanizomenon flosaquae and Arthrospira platensis (Spirulina). [
Health Risks • Cyanobacteria can produce toxins which are called cyanotoxins • Cyanobacteria reproduce explosively under certain conditions. • This results in algal blooms, which can become harmful to other species, and pose a danger to humans and animals
Anabena have mutualist relationship with an aquatic fern azolla in rice fields Anabena cell in large filamentous colonies with no gelatinous matrix. Heterocysts and akinetes are present
Microcystis- cells in large colonies irregularly arranged in gelatinous matrix
Lyngbay Unbranched filaments with extended sheets beyond the filaments Heterocyst and akinets are absent
Oscillataria – un branched filaments with no conspicuous sheath extension
Stigonema A cyanobacteria with true branching and heterocyst
Scytonema Have false branching – filaments arise from same sheath
DONE
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