Cyanobacteria and their uses

 

      Cyanobacteria are microscopic microorganisms, unicellular or multicellular oxygenic photoautotrophs, and Gram-negative prokaryotes, widespread in terrestrial or aquatic environment and mostly occur in fresh water and marine environment. Cyanobacteria constitute a phylogenetically coherent group of evolutionarily ancient, morphologically diverse, and ecologically important phototrophic bacteria, claims Science Direct. Classification of cyanobacteria proposed in 1985, in which four orders of the bacteria have been identified as Chroococcales, Nostocales, Oscillatoriales and Stigonematales, and their phyla are Chroococcales, Gloeobacterales, and Pleurocapsales, allegedly, claims an article from Science Direct. They are defined by their ability to carry out oxygenic photosynthesis (water-oxidizing, oxygen-evolving, plant-like photosynthesis). With few exceptions, they synthesize chlorophyll a as major photosynthetic pigment and phycobiliproteins as light-harvesting pigments. All are able to grow using CO₂ as the sole source of carbon, which they fix using primarily the reductive pentose phosphate pathway. Five types of cyanobacteria have been identified as toxin producers, including two strains of Anabaena flosaquae, Aphanizomenon flosaquae, Microcystis aeruginosa and Nodularia species. Cyanobacterial toxins are of three main types: hepatotoxins, neurotoxins and lipopolysaccharide (LPS) endotoxins.

      Acute illness following consumption of drinking water contaminated by cyanobacteria is more commonly gastroenteritis. Cyanobacteria are not dependent on a fixed source of carbon and, as such, are widely distributed throughout aquatic environments. These include freshwater and marine environments and in some soils. Direct microscopic examination of bloom material will allow identification of the cyanobacterial species present. Preventing the formation of blooms in the source water is the best way to assure cyanobacteria-free drinking water and membrane filtration technology has the potential to remove virtually any cyanobacteria or their toxins from drinking water. Cyanobacteria have the ability to grow as biofilms. Allegedly their chemoorganotrophic potential is restricted to the mobilization of reserve polymers (mainly glycogen) during dark periods, although some strains are known to grow chemoorganotrophically in the dark at the expense of external sugars. Cyanobacteria have left fossil remains as old as 2000–3500 million years, and they are believed to be ultimately responsible for the oxygenation of Earth’s atmosphere. During their evolution, through an early symbiotic partnership, they gave rise to the plastids of algae and higher plants. As a group, they display some of the most sophisticated morphological differentiation among the bacteria, and many species are truly multicellular organisms.Today cyanobacteria make a significant contribution to the global primary production of the oceans and become locally dominant primary producers in many extreme environments, such as hot and cold deserts, hot springs, and hypersaline environments. Their global biomass has been estimated to exceed 10¹⁵ g of wet biomass, most of which is accounted for by the marine unicellular genera Prochlorococcus and Synechococcus, the filamentous genera Trichodesmium (a circumtropical marine form), as well as the terrestrial Microcoleus vaginatus and Chroococcidiopsis sp. of barren lands. Blooms of cyanobacteria are important features for the ecology and management of many eutrophic fresh and brackish water bodies.

      Cyanobacteria are very well equiped, resourceful, old, prolific and important lifeforms, and can be very useful to human regulated agriculture and health and medicine amongst other things.Continuous increase in global human population and depletion of natural resources of energy posing threat to environment needs, sustainable supply of food and energy. The most ecofriendly approach ‘green technology’ has been exploited for biofertilizer preparation. Cyanobacteria are the most successful and sustained prokaryotic organism during the course of evolution. They are considered as one of the primitive life forms found on our planet. Cyanobacteria are emerging candidates for efficiently conversion of radiant energy into chemical energy. This biological system produces oxygen as a by-product. Cyanobacterial biomass can also be used for the large scale production of food, energy, biofertilizers, secondary metabolites, cosmetics and medicines. Microbial secondary metabolites are low-molecular-mass products of secondary metabolism, usually produced during the late growth phase (idiophase) of microorganisms. They have unusual structures and their production arises from intracellular intermediates (amino acids, sugars, fatty acids, etc.), which are condensed into more complex structures by defined biochemical pathways. They are not essential for the growth of the producing cultures, but serve diverse survival functions in nature. They are very important for the human health and economics.They include antibiotics, antitumor agents, cholesterol-lowering drugs, immunosuppressants, antihelmintic agents and other antiparasitics, herbicides, ruminant growth stimulators, agricultural fungicides, bio-insecticides, and others. The most important secondary metabolites have been the anti-infective drugs and, among these, the β-lactams are the most important class. Other important classes include the aminoglycosides, tetracyclines, macrolides, lipopeptides, polyenes, and the echinocandins. Successful microbial secondary metabolites include many used to combat cancer, such as the anthracycline doxorubicin and bleomycin. Antitumor agents from plants that have been very useful are taxol and camptothecin.