Nitrogen fixation is a chemical process by which molecular nitrogen (N
2), which has a strong triple covalent bond, is converted into ammonia (NH
3) or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif).
Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" refers to their cyan color, which forms the basis of cyanobacteria's informal common name, blue-green algae, although as prokaryotes they are not scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment.
Phycocyanin is a pigment-protein complex from the light-harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin. It is an accessory pigment to chlorophyll. All phycobiliproteins are water-soluble, so they cannot exist within the membrane like carotenoids can. Instead, phycobiliproteins aggregate to form clusters that adhere to the membrane called phycobilisomes. Phycocyanin is a characteristic light blue color, absorbing orange and red light, particularly near 620 nm, and emits fluorescence at about 650 nm. Allophycocyanin absorbs and emits at longer wavelengths than phycocyanin C or phycocyanin R. Phycocyanins are found in cyanobacteria. Phycobiliproteins have fluorescent properties that are used in immunoassay kits. Phycocyanin is from the Greek phyco meaning “algae” and cyanin is from the English word “cyan", which conventionally means a shade of blue-green and is derived from the Greek “kyanos" which means a somewhat different color: "dark blue". The product phycocyanin, produced by Aphanizomenon flos-aquae and Spirulina, is for example used in the food and beverage industry as the natural coloring agent 'Lina Blue' or 'EXBERRY Shade Blue' and is found in sweets and ice cream. In addition, fluorescence detection of phycocyanin pigments in water samples is a useful method to monitor cyanobacteria biomass.
Synechococcus is a unicellular cyanobacterium that is very widespread in the marine environment. Its size varies from 0.8 to 1.5 μm. The photosynthetic coccoid cells are preferentially found in well–lit surface waters where it can be very abundant. Many freshwater species of Synechococcus have also been described.
Cyanophages are viruses that infect cyanobacteria, also known as Cyanophyta or blue-green algae. Cyanobacteria are a phylum of bacteria that obtain their energy through the process of photosynthesis. Although cyanobacteria metabolize photoautotrophically like eukaryotic plants, they have prokaryotic cell structure. Cyanophages can be found in both freshwater and marine environments. Marine and freshwater cyanophages have icosahedral heads, which contain double-stranded DNA, attached to a tail by connector proteins. The size of the head and tail vary among species of cyanophages. Cyanophages infect a wide range of cyanobacteria and are key regulators of the cyanobacterial populations in aquatic environments, and may aid in the prevention of cyanobacterial blooms in freshwater and marine ecosystems. These blooms can pose a danger to humans and other animals, particularly in eutrophic freshwater lakes. Infection by these viruses is highly prevalent in cells belonging to Synechococcus spp. in marine environments, where up to 5% of cells belonging to marine cyanobacterial cells have been reported to contain mature phage particles.
Synechocystis sp. PCC6803 is a strain of unicellular, freshwater cyanobacteria. Synechocystis sp. PCC6803 is capable of both phototrophic growth by oxygenic photosynthesis during light periods and heterotrophic growth by glycolysis and oxidative phosphorylation during dark periods. Gene expression is regulated by a circadian clock and the organism can effectively anticipate transitions between the light and dark phases.
Cyanobionts are cyanobacteria that live in symbiosis with a wide range of organisms such as terrestrial or aquatic plants; as well as, algal and fungal species. They can reside within extracellular or intracellular structures of the host. In order for a cyanobacterium to successfully form a symbiotic relationship, it must be able to exchange signals with the host, overcome defense mounted by the host, be capable of hormogonia formation, chemotaxis, heterocyst formation, as well as possess adequate resilience to reside in host tissue which may present extreme conditions, such as low oxygen levels, and/or acidic mucilage. The most well-known plant-associated cyanobionts belong to the genus Nostoc. With the ability to differentiate into several cell types that have various functions, members of the genus Nostoc have the morphological plasticity, flexibility and adaptability to adjust to a wide range of environmental conditions, contributing to its high capacity to form symbiotic relationships with other organisms. Several cyanobionts involved with fungi and marine organisms also belong to the genera Richelia, Calothrix, Synechocystis, Aphanocapsa and Anabaena, as well as the species Oscillatoria spongeliae. Although there are many documented symbioses between cyanobacteria and marine organisms, little is known about the nature of many of these symbioses. The possibility of discovering more novel symbiotic relationships is apparent from preliminary microscopic observations.
Bacterial circadian rhythms, like other circadian rhythms, are endogenous "biological clocks" that have the following three characteristics: (a) in constant conditions they oscillate with a period that is close to, but not exactly, 24 hours in duration, (b) this "free-running" rhythm is temperature compensated, and (c) the rhythm will entrain to an appropriate environmental cycle.
CandidatusAtelocyanobacterium thalassa, also referred to as UCYN-A, is a diazotrophic species of cyanobacteria commonly found in measurable quantities throughout the world's oceans and some seas. Members of A. thalassa are spheroid in shape and are 1-2 μm in diameter, and provide nitrogen to ocean regions by fixing non biologically available atmospheric nitrogen into biologically available ammonium that other marine microorganisms can use.
In molecular biology, Cyanobacterial non-coding RNAs are non-coding RNAs which have been identified in species of cyanobacteria. Large scale screens have identified 21 Yfr in the marine cyanobacterium Prochlorococcus and related species such as Synechococcus. These include the Yfr1 and Yfr2 RNAs. In Prochlorococcus and Synechocystis, non-coding RNAs have been shown to regulate gene expression. NsiR4, widely conserved throughout the cyanobacterial phylum, has been shown to be involved in nitrogen assimilation control in Synechocystis sp. PCC 6803 and in the filamentous, nitrogen-fixing Anabaena sp. PCC 7120.
Cyanothece is a genus of unicellular, diazotrophic, oxygenic photosynthesizing cyanobacteria.
kaiA is a gene in the "kaiABC" gene cluster that plays a crucial role in the regulation of bacterial circadian rhythms, such as in the cyanobacterium Synechococcus elongatus. For these bacteria, regulation of kaiA expression is critical for circadian rhythm, which determines the twenty-four-hour biological rhythm. In addition, KaiA functions with a negative feedback loop in relation with kaiB and KaiC. The kaiA gene makes KaiA protein that enhances phosphorylation of KaiC while KaiB inhibits activity of KaiA.
Orange carotenoid protein (OCP) is a water-soluble protein which plays a role in photoprotection in diverse cyanobacteria. It is the only photoactive protein known to use a carotenoid as the photoresponsive chromophore. The protein consists of two domains, with a single keto-carotenoid molecule non-covalently bound between the two domains. It is a very efficient quencher of excitation energy absorbed by the primary light-harvesting antenna complexes of cyanobacteria, the phycobilisomes. The quenching is induced by blue-green light. It is also capable of preventing oxidative damage by directly scavenging singlet oxygen (1O2).
Crocosphaera watsonii is an isolate of a species of unicellular diazotrophic marine cyanobacteria which represent less than 0.1% of the marine microbial population. They thrive in offshore, open-ocean oligotrophic regions where the waters are warmer than 24 degrees Celsius. Crocosphaera watsonii cell density can exceed 1,000 cells per milliliter within the euphotic zone; however, their growth may be limited by the concentration of phosphorus. Crocosphaera watsonii are able to contribute to the oceanic carbon and nitrogen budgets in tropical oceans due to their size, abundance, and rapid growth rate. Crocosphaera watsonii are unicellular nitrogen fixers that fix atmospheric nitrogen to ammonia during the night and contribute to new nitrogen in the oceans. They are a major source of nitrogen to open-ocean systems. Nitrogen fixation is important in the oceans as it not only allows phytoplankton to continue growing when nitrogen and ammonium are in very low supply but it also replenishes other forms of nitrogen, thus fertilizing the ocean and allowing more phytoplankton growth.
Trichodesmium thiebautii is a cyanobacteria that is often found in open oceans of tropical and subtropical regions and is known to be a contributor to large oceanic surface blooms. This microbial species is a diazotroph, meaning it fixes nitrogen gas (N2), but it does so without the use of heterocysts. T. thiebautii is able to simultaneously perform oxygenic photosynthesis. T. thiebautii was discovered in 1892 by M.A. Gomont. T. thiebautii are important for nutrient cycling in marine habitats because of their ability to fix N2, a limiting nutrient in ocean ecosystems.
SbtB, which stands for sodium-bicarbonate-transporter B, is a protein found in bacteria. This small soluble protein has been classified as a new member of the P-II family that is involved in signal transduction. This protein has been demonstrated to participate in numerous processes including carbon sensing mechanisms in cyanobacteria.
Microbial DNA barcoding is the use of DNA metabarcoding to characterize a mixture of microorganisms. DNA metabarcoding is a method of DNA barcoding that uses universal genetic markers to identify DNA of a mixture of organisms.
A plastid is a membrane-bound organelle found in plants, algae and other eukaryotic organisms that contribute to the production of pigment molecules. Most plastids are photosynthetic, thus leading to color production and energy storage or production. There are many types of plastids in plants alone, but all plastids can be separated based on the number of times they have undergone endosymbiotic events. Currently there are three types of plastids; primary, secondary and tertiary. Endosymbiosis is reputed to have led to the evolution of eukaryotic organisms today, although the timeline is highly debated.
Richelia is a genus of nitrogen-fixing, filamentous, heterocystous and cyanobacteria. It contains the single species Richelia intracellularis. They exist as both free-living organisms as well as symbionts within potentially up to 13 diatoms distributed throughout the global ocean. As a symbiont, Richelia can associate epiphytically and as endosymbionts within the periplasmic space between the cell membrane and cell wall of diatoms.
Cyanobacterial morphology refers to the form or shape of cyanobacteria. Cyanobacteria are a large and diverse phylum of bacteria defined by their unique combination of pigments and their ability to perform oxygenic photosynthesis.
