L14 - Cyanobacteria Flashcards
What are cyanobacteria?
They are large, morphologically, ecologically heterogeneous group of oxygenic, phototrophic bacteria.
What is the difference in DNA dispersion in cyanobacteria prokaryotic cells?
DNA dispersed within cell, photosynthetic lamellae occur freely in the cytoplasm.
What is the difference in DNA dispersion in cyanobacteria eukaryotic cells?
DNA localised within a nucleus; essentially similar to those of higher plants. Photosynthetic lamellae are confined within membranes as well as defined chloroplasts
What are cyanobacteria on?
A bacterial phylum, phylogenetic tree of the major phyla of cultivated bacteria.
What are cyanobacteria?
Blue-green algae. Gram-negative bacteria. Only photosynthetic prokaryotes to produce O2. 0.2 - 2 um, but can be 40 um in diameter. Characteristic colour: phycocyanin. Extremely diverse (in freshwater, marine, terrestrial and extreme environments.
Why are cyanobacteria important?
Pivotal to life on earth - important in evolutionary history. First time oxygen found in the atm ~ 2.5 billion years ago. Without them there would be no plants and no us… no life.
What is the evolutionary importance of cyanobacteria?
2.8 to 2.5 billion years old. Important in shaping evolutionary change throughout earth’s history. First organisms capable of oxygenic photosynthesis. Main driving force in converting a very reducing and anaerobic atmosphere to one with oxygen.
What are stromatolites?
Rock like structures made of cyanobacteria. Earth’s oldest fossil - important in informing on evolution. Stromatolites are modern-day examples of life in precambrian times.
How are prokaryotes pivotal to the evolution of life?
Prokaryotes gave rise to the first eukaryotic cells via endosymbiosis. Phagotrophic cell came along, engulfed cyanobacteria which then became the chloroplast in eukaryotes.
What happens in further endosymbiosis?
The number of membranes help determine classification. However, still topic of research
Tree of eukaryotes?
Algae have evolved many times in the tree of life. Higher plants just the once from green algae. Very diverse in their form and function. Fungi, bacteria, cyanobacteria, animals all come off on single branches. We don’t have a good single definition for algae because its evolution is so broad
What is the physiology of cyanobacteria?
Oxygenic phototrophs with both FeS and Q-type photosystems. All fix CO2 by the calvin cycle. Many fix N2. Most synthesise own vitamins. Harvest energy from light and fix CO2 during day. Generate energy by fermentation or aerobic respiration of carbon storage products (e.g. glycogen) at night. Some can assimilate simple organic compounds in light (photoheterotrophy). Some can switch to anoxygenic photosynthesis using H2S as electron donor.
What is inside a cyanobacterial cell?
Ribosomes, thylakoids, nucleoid (DNA ring), RuBisCO, carboxysome, slime coat, capsule, mucoid sheath, peptidoglycan layer, outer membrane, cell membrane, cell wall, phycobilisome, thylakoid membrane
What are thylakoids?
Specialised membrane systems that increase ability to harvest light energy, typically arranged in concentric circles around cytoplasm periphery.
What is the physiology of photosynthetic membranes?
Cyanobacteria produce pigments: chlorophyll a, phycobilins (accessory pigments) - Phycocyanin are blue making together with chlorophyll a the blue-green colour of cyanobacteria. Phycoerthryin is a red phycobilin making the producer species red or brown. Prochlorophytes (e.g. Prochlorococcus and Prochloron) contain chlorophyll a and b but no phycobilins.
Photosynthesis in cyanobacteria?
In addition to photosystems 1 and 2, cyanobacteria contain phycobilisomes which contain phycoerythrin and phycocyanin
Chloroplasts vs cyanobacteria?
Chloroplasts - intermembrane space (viridiplantaean chloroplasts and rhodoplasts), granum (higher plants)
Shared - outer membrane, inner membrane, nucleoid, thylakoids, lipid droplet, ribosomes.
Cyanobacterium - peptidoglycan wall (also in muroplasts), mucoid sheath, capsule, slime coat.
What is the cell structure and motility of cyanobacteria?
Cell walls contain peptidoglycan, possess several motility mechanisms but no flagella. Many cyanobacteria display gliding motility when in contact with solid surface, another cell, or filament. Most show phototaxis (towards light); chemotaxis may occur.
What is the function of gas vesicles?
Regulate buoyancy important in positioning in water column where light intensity is optimal. Many produce sheaths (mucilaginous envelopes) that bind groups of cells or filaments together. Some form hormogonia (short, motile filaments that break off to facilitate dispersal under stress). There is no sexual reproduction in cyanobacteria. Some form akinetes (resting structures with thickened outer walls that protect the organism from darkness, desiccation or cold. Many form cyanophycin (nitrogen storage product). Many form Nostocales and Stigonematales form heterocysts.
What is nitrogenase?
It is sensitive to oxygen, so fixation cannot occur along with oxygenic photosynthesis. Several regulatory mechanisms separate nitrogenase from photosynthesis - many unicellular cyanobacteria fix nitrogen only at night, some transiently suppress photosynthetic activity within filaments, many filamentous cyanobacteria form heterocysts.
What are heterocysts?
Arise from differentiation of vegetative cells, surrounded by thickened cell wall that slows diffusion of O2 and provides an anoxic environment. Lack photosystem, cannot fix CO2. Fixed carbon is imported from adjacent cells and oxidised to yield electrons for nitrogen fixation. Fixed nitrogen moves to vegetative cells.
Heterocysts & Nitrogen fixation - types of microscopy?
Phase contrast and fluorescence microscopy.
What are the different types of cells in filamentous cyanobacteria?
Akinete (resting stage with granular - thick wall), Heterocysts (nitrogen fixation), hormogonia.
What is the ecology of cyanobacteria?
Important for productivity of oceans - Synechococcus and Prochlorococcus are most abundant ocean phototrophs, contributing 80 percent of marine photosynthesis and 35 percent of total photosynthesis. Cyanobacterial nitrogen fixation is dominant input of new nitrogen in oceans.
Nitrogen fixation in cyanobacteria in the oceans?
Many cyanobacteria are capable of fixing N, converting atmospheric N into nitrate or ammonia. In habitats like Artic regions where N is a limiting element, they can contribute up to 80% of annual N input.
Nitrogen fixation in cyanobacteria - in rice paddy fields?
Anabaena and Nostoc species. Long filamentous algae.
What else is the ecology of cyanobacteria?
Also widely distributed in terrestrial, marine and freshwater environments - more tolerant of extremes than eukaryotic algae (e.g. hot springs, saline lakes, desert soils), develop freshwater lake blooms, can be symbionts. Important metabolic products (e.g. potent neurotoxins and toxic blooms, geosmin in water).
Cyanobacteria as extremophiles?
Their metabolism and lifestyle is very flexible, survive extremely high & low temperatures (-2 degC to 70 degC). Impressive ability to colonise infertile substrates e.g. volcanic ash, desert sand & rocks.
Cyanobacteria symbiosis with plants?
Cyanobacteria form symbiotic associations with a wide range of eukaryotic hosts including plants, fungi, sponges, ascidians and protists. E.g. gunnera plant - in singleton park.
What else are cyanobacteria symbiotic with?
Fungi in lichens
Cyanobacteria as marine symbionts?
Abundant in coral reefs, common hosts: sponges & ascidians. Also a factor preventing recovery from coral reef phase shifts. Cyanobacteria help build reefs, form a major component of epiphytic, epilithic, and endolithic communities as well as of microbial mats. Provide nitrogen through nitrogen fixation.
Cyanobacteria in microbial mats and biofilms?
They can form an important part of microbial mats or biofilms in terrestrial and aquatic ecosystems, along with bacteria and archaea. Can see them on pipes, in gardens, boggy areas etc. Given away by the colour - blue green is cyanobacteria.
What is there in cyanobacteria?
Impressive morphological diversity. Unicellular, colonies or filamentous with specialised cells. Range from 0.5 to 100um in diameter, five morphological groups. Less diverse in form than eukaryotic algae but rich in chemical diversity
What are the chroococcales?
Unicellular, divide by binary fission; includes prochlorophytes (unique, unicellular)
What are the Pleurocapsales?
Unicellular, dividing by multiple fission (colonial)
What are the Oscillatoriales?
Filamentous nonheterocystous
What are the Nostocales?
Filamentous, divide on single axis, can differentiate
What are the Stigonematales?
Filamentous, divide in multiple planes, forming branching filaments
What is Synechocystis Sp. PCC 6803?
Unicellular spherical cells. Binary fission, found in freshwater.
Why is Synechocystis Sp. PCC 6803 so important?
Model cyanobacterium, first photosynthetic organism to have its entire genome sequenced - 1996. Autotrophic and heterotrophic growth. Gene expression regulated by a circadian clock - predicts light - dark
What is Synechococcuss?
Unicellular, prokaryotic autotrophic picoplankton. Discovered in the sea in 1979!. Abundant in the world’s oceans. Also many freshwater strains. Main source of primary production in oligotrophic, pelagic marine waters. Major primary producers on a global scale.
What are the size of Nanoeukaryotes, Picoeukaryotes, Picoprokaryotes?
2-20um, 0.2-2um, 0.2-2um
What are the picoplankton?
Prochlorococcus and synechococcus are not the only picoplankton. New picoplanktonic eukaryotic algal class: Bolidophyceae.
What are prochlorococcus?
Component of the picoplankton : picoprokaryotes. Discovered recently in 1988. Smallest & most abundant photosynthetic organism on earth. Major importance in the ocean. Different ecotypes. Unusual chlorophylls - divinyl chlorophyll-a and b.
Where is the global abundance of prochlorococcus and synechococcus?
Quantitatively the most important organisms on earth. >25% of net primary production in the oceans
What is Trichodesmium (sea sawdust)?
Filamentous cyanobacteria. Trichodesmium sp. is non-heterocystous cyanobacteria. Widespread in tropical & subtropical seas. Fixes N2 without heterocysts i.e. occurs aerobically. Gas vesicles regulate buoyancy in the water column
What is Spirulina (Arthrospira platensis)?
Freshwater, well known species, occurs naturally in tropical and subtropical lakes with high pH. Large commercial production. 65-71% protein.
What is Nostacales: Anabaena and Nostoc?
Colonial filamentous - hair like trichomes. Terrestrial or freshwater species. Forms loose clumps on soil, gravel and paved surfaces, among mosses and between cobbles. Can survive in extreme conditions: Polar & arid areas.
What cyanobacteria are toxic?
Some freshwater species are toxic and can cause major problems in lakes and reservoirs. Anabaena flosaquae - ‘anatoxin’. Microcystis - ‘microcystin’. Aphanizomenon flosaquae - ‘saxitoxin’. Recent discovery - widespread across cyanobacteria - BMAA (Beta-N-methylamino-L-alanine)
What is different in the different toxic species?
Different toxin molecules.
What are toxic blooms of cyanobacteria in baltic sea: microcystins - hepatotoxic?
Filamentous cyanobacteria: Nodularia spumigena. Occurs every year late summer: phosphate in the surface water, temperature and weather conditions are important factors
What is BMAA?
A more recently discovered neurotoxin, Beta-methylamino-L-alanine or 2-Amino-3-(methylamino)propanoic acid. Widespread in terrestrial, but also marine cyanobacteria. BMAA can cause neurodegenerative disease like Alzheimer’s and possibly motor neurone disease.
What are some cyanobacterial anticancer drug candidates?
Malyngamide 2, Dolastatin 10, Cylindrospermopsin, synthetic analogue of crytptophycin
What is Malynamide 2?
Natural product isolated from the cyanobacterium Lyngbya majuscula that has shown potent anticancer activity in preclinical studies. A clinical trial was conducted to investigate its safety and efficacy for the treatment of solid tumours, but the results have not yet been published.
What is Dolastatin 10?
Natural product, isolated from the cyanobacterium Symploca, that has shown potential anticancer activity. It has been investigated in several clinical trials for the treatment of various types of cancer, including breast, lung, and melanoma
What is Cylindrospermopsin?
A toxic natural product, produced by various cyanobacteria that has been investigated for its potential as an anticancer agent. Several preclinical studies have shown that it has potent anticancer activity against various types of cancer cells, but clinical trials have not yet been conducted
What is Cryptophycin?
Synthetic analogue of cryptophycin isolated from terrestrial cyanobacteria progressed to Phase 2 clinical trials for the treatment of patients with platinum-resitant ovarian cancer.
Cyanobacteria and biotechnology?
Have minimal nutritional requirements. Higher photosynthetic efficiency in terms of sunligh conversion into biomass and growth rates than all other photosynthetic organisms. Cyanobacteria have been used as food sources and biofertilisers for centuries. Through N2 fixation they improve the fertility of rice-fields and many soils. They produce a broad spectrum of high value compounds.
