| Cylindrospermopsis raciborskii | |
|---|---|
Scientific classification  | |
| Domain: | Bacteria |
| Phylum: | Cyanobacteria |
| Class: | Cyanophyceae |
| Order: | Nostocales |
| Family: | Aphanizomenonaceae |
| Genus: | Cylindrospermopsis |
| Species: | C. raciborskii |
| Binomial name | |
| Cylindrospermopsis raciborskii (Woloszynska) Seenaya & Subbaraju | |
Cylindrospermopsis raciborskii is a freshwater cyanobacterium. (name currently accepted taxonomically: Raphidipsis raciborskii)
This bacterium is an aquatic photosynthetic bacteria belonging to the phylum Cyanobacteria. They are composed of chained filaments known as trichomes that can show variation in morphology, varying from about 50–300 micrometers in length. [1] These bacteria can also produce a thick walled, cylindrical, spore like structure known as akinetes, which also demonstrate variation in morphology. Some strains of this species are able to produce several toxins which affect humans: cylindrospermopsin, anatoxin-a and saxitoxin. [1] This first toxin, cylindrospermopsin, has the ability to affect the liver and kidneys in humans as well as cause mild skin reactions upon exposure. [1] The last two toxins, anatoxin-a and saxitoxin, are thought to be shellfish neurotoxins. Research has shown that C. raciborskii can naturally produce butylated hydroxytoluene, an antioxidant, food additive, and industrial chemical. [2]
Domain – Bacteria
The Tree of Life contains three Domains: Bacteria, Archaea, and Eukaryota.
Kingdom – Bacteria
Bacteria consists of prokaryotic microorganisms. They were among the first life forms to appear on Earth and appear in a wide variety of habitats.
Phylum – Cyanobacteria
This phylum is characterized by their ability to obtain energy through photosynthesis. They are often called the blue-green algae stemming from the Greek origins of the word kyanós, meaning blue.
Class – Cyanophyceae [3]
This class consists of photosynthetic bacteria found in fresh and salt water, containing chlorophyll a and phycobilins.
Order – Nostocales
This order includes cyanobacteria of filamentous forms, either simple or branched, both of which occur as single strands or multiple strands within a sheath.
Family – Nostocaceae
This family of cyanobacteria forms filament-shaped colonies enclosed in mucus or a gelatinous sheath. Their habitats vary widely ranging from fresh water to salt water conditions. They often contain photosynthetic pigments in their cytoplasm to perform photosynthesis, which gives the cells a bluish-green color.
Genus – Cylindrospermopsis
This genus of filamentous cyanobacteria is found in terrestrial and aquatic environments. In terrestrial ecosystems, Cylindrospermum is found in soils, while in aquatic it commonly grows as part of the periphyton on aquatic plants. The particular genus is a heterocystous (nitrogen-fixing) cyanobacterium.
Species – Cylindrospermopsis raciborskii
This bacterium is a freshwater cyanobacterium often found in tropical regions but can be also found in more temperate locations such as the Great Lakes located in North America. [1] The bacterium has the ability to fix atmospheric nitrogen as well as absorb and store phosphorus. [1] These abilities are advantageous to its survival in deep bodies of water where it has to compete for light. Under environmental stresses such as cool temperatures or low nutrients the bacteria has the ability to form its spore like structure known as akinetes. These akinetes can persist in sediment for long periods of time, and are able to germinate once water temperatures rise to the appropriate level. [1] The bacteria prefers temperatures ranging from 25–30 °C, light intensity of 80–121 μmol m-2 s-1, and a max salinity concentration of 4 g L-1 NaCl. The levels of the bacteria typically stay relatively low throughout the summer, however it can be associated with very high concentrations under certain conditions. These conditions include: low flow; low water level; low nitrogen to phosphorus ratio; high water temperature; stable thermal stratification; increased retention time; high pH; high sulfate concentration; anoxia in at least some strata; high turbidity; high incident irradiation; and low macrophyte biomass. [1]
The bacterium is thought to have originated in tropical or sub tropical regions. However, the bacteria has recently been discovered in more temperate climates such as the Great Lakes in North America. [1] The strain found in North America is thought to have originated in South America and it is believed that climate change is a factor behind the expansion of the bacteria's environment. So far there have been no documented effects of the species being present in the Great Lakes. [1] However, this bacterium has been linked to liver damage and even death in humans after the contamination of water supplies. It has also been linked to fish kills in Brazil, cattle death in Australia, reduction of zooplankton in Florida, as well as toxicity to some shellfish, which it accumulates in organisms such as crawfish. [1]
Cylindrospermopsis raciborskii is a filamentous cyanobacteria with the ability to fix nitrogen by converting atmospheric nitrogen (N2) into ammonia (NH3), thus distinguishing it as a heterocyst. [4] It provides the cells in the filament with nitrogen for biosynthesis by fixing nitrogen from dinitrogen (N2) using the enzyme nitrogenase. Normally, nitrogenase is inactivated by oxygen, which forces the bacterium to operate in a microanaerobic environment. The heterocyst's unique structure and physiology requires a global change in gene expression. This includes a variety of mechanisms including, but not limited to:
Cylindrospermopsis raciborskii obtains its fixed carbon via photosynthesis. The lack of photosystem II would normally prevent it from photosynthesizing, but the vegetative cells provide the necessary carbohydrates, which is thought to be sucrose. The fixed carbon and nitrogen sources are exchanged through channels between the cells in the filament. C. raciborskii does maintain photosystem I, allowing it to generate ATP by cyclic photophosphorylation.
The mechanism of controlling this nitrogen fixation pathway is thought to involve the diffusion of an inhibitor of differentiation called patS. Heterocyst formation is inhibited in the presence of a fixed nitrogen source, such as ammonium or nitrate. Therefore, maintenance is dependent on an enzyme called hetN. An alternate method involves the bacteria entering a symbiotic relationship with certain plants. In such relationships, the bacteria does not respond to the availability of nitrogen, but rather to signals produced by the plant. In this method, up to 60% of the cells can become heterocystic, providing fixed nitrogen to the plant in return for fixed carbon.
The appearance of cyanobacteria in water storage bodies is becoming of increasing importance and is a major factor in the eutrophication of rivers and streams. Many times the effects of the bacteria's presence can be toxic for livestock and wildlife, as well as for humans. [5] Its exact mode of virulence, however, is still unknown. It has been narrowed down that its virulence is primarily hepatotoxic, although other organs such as the kidneys can be involved.
It is known that Cylindrospermopsis raciborskii has the ability to tolerate a rather wide range of climatic conditions. Its ability to produce akinetes assures survival even under harsher winter conditions. The population dynamics is highly dependent on lake water temperature and underwater light intensity and thus on climatic conditions. [6] Therefore, any future increase in lake water temperature will presumably lead to an increase in the size of C. raciborskii populations in eutrophic lakes posing an increased threat to drinking water supply.
In 1979, Cylindrospermopsis raciborskii was attributed with causing hepatoenteritis (an infection of the liver resembling hepatitis) in 148 people off the northern coast of Queensland at Palm Island. [7] The contamination of drinking water was attributed to copper sulfate treatment in the island's drinking-water supply, Solomon Dam. The copper sulfate was intended to control a dense algal bloom. However, copper sulfate causes lysis of cyanobacteria, leading to the release of any toxic cellular components. It was determined after an investigation that the contaminated water was all from Solomon Dam where the copper sulfate was applied. It was during this investigation that C. raciborskii was first identified as a pathogen.
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 gram-negative bacteria that obtain energy via photosynthesis. The name cyanobacteria refers to their color, which similarly forms the basis of cyanobacteria's common name, blue-green algae, although they are not usually scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment. Sericytochromatia, the proposed name of the paraphyletic and most basal group, is the ancestor of both the non-photosynthetic group Melainabacteria and the photosynthetic cyanobacteria, also called Oxyphotobacteria.
Hormogonia are motile filaments of cells formed by some cyanobacteria in the order Nostocales and Stigonematales. They are formed during vegetative reproduction in unicellular, filamentous cyanobacteria, and some may contain heterocysts and akinetes.
Trichodesmium, also called sea sawdust, is a genus of filamentous cyanobacteria. They are found in nutrient poor tropical and subtropical ocean waters. Trichodesmium is a diazotroph; that is, it fixes atmospheric nitrogen into ammonium, a nutrient used by other organisms. Trichodesmium is thought to fix nitrogen on such a scale that it accounts for almost half of the nitrogen fixation in marine systems globally. Trichodesmium is the only known diazotroph able to fix nitrogen in daylight under aerobic conditions without the use of heterocysts.
Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale, and Anabaena sphaerica. They fix nitrogen from dinitrogen (N2) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis.
Diazotrophs are bacteria and archaea that fix gaseous nitrogen in the atmosphere into a more usable form such as ammonia.
Anabaena is a genus of filamentous cyanobacteria that exist as plankton. They are known for nitrogen-fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to local wildlife, as well as farm animals and pets. Production of these neurotoxins is assumed to be an input into its symbiotic relationships, protecting the plant from grazing pressure.
Algal mats are one of many types of microbial mat that forms on the surface of water or rocks. They are typically composed of blue-green cyanobacteria and sediments. Formation occurs when alternating layers of blue-green bacteria and sediments are deposited or grow in place, creating dark-laminated layers. Stromatolites are prime examples of algal mats. Algal mats played an important role in the Great Oxidation Event on Earth some 2.3 billion years ago. Algal mats can become a significant ecological problem, if the mats grow so expansive or thick as to disrupt the other underwater marine life by blocking the sunlight or producing toxic chemicals.
Anabaena circinalis is a species of Gram-negative, photosynthetic cyanobacteria common to freshwater environments throughout the world. Much of the scientific interest in A. circinalis owes to its production of several potentially harmful cyanotoxins, ranging in potency from irritating to lethal. Under favorable conditions for growth, A. circinalis forms large algae-like blooms, potentially harming the flora and fauna of an area.
Cylindrospermopsin is a cyanotoxin produced by a variety of freshwater cyanobacteria. CYN is a polycyclic uracil derivative containing guanidino and sulfate groups. It is also zwitterionic, making it highly water soluble. CYN is toxic to liver and kidney tissue and is thought to inhibit protein synthesis and to covalently modify DNA and/or RNA. It is not known whether cylindrospermopsin is a carcinogen, but it appears to have no tumour initiating activity in mice.
An akinete is an enveloped, thick-walled, non-motile, dormant cell formed by filamentous, heterocyst-forming cyanobacteria under the order Nostocales and Stigonematales. Akinetes are resistant to cold and desiccation. They also accumulate and store various essential material, both of which allows the akinete to serve as a survival structure for up to many years. However, akinetes are not resistant to heat. Akinetes usually develop in strings with each cell differentiating after another and this occurs next to heterocysts if they are present. Development usually occurs during stationary phase and is triggered by unfavorable conditions such as insufficient light or nutrients, temperature, and saline levels in the environment. Once conditions become more favorable for growth, the akinete can then germinate back into a vegetative cell. Increased light intensity, nutrients availability, oxygen availability, and changes in salinity are important triggers for germination. In comparison to vegetative cells, akinetes are generally larger. This is associated with the accumulation of nucleic acids which is important for both dormancy and germination of the akinete. Despite being a resting cell, it is still capable of some metabolic activities such as photosynthesis, protein synthesis, and carbon fixation, albeit at significantly lower levels.
Aphanizomenon is a genus of cyanobacteria that inhabits freshwater lakes and can cause dense blooms. They are unicellular organisms that consolidate into linear (non-branching) chains called trichomes. Parallel trichomes can then further unite into aggregates called rafts. Cyanobacteria such as Aphanizomenon are known for using photosynthesis to create energy and therefore use sunlight as their energy source. Aphanizomenon bacteria also play a big role in the Nitrogen cycle since they can perform nitrogen fixation. Studies on the species Aphanizomenon flos-aquae have shown that it can regulate buoyancy through light-induced changes in turgor pressure. It is also able to move by means of gliding, though the specific mechanism by which this is possible is not yet known.
Planktothrix is a diverse genus of filamentous cyanobacteria observed to amass in algal blooms in water ecosystems across the globe. Like all Oscillatoriales, Planktothrix species have no heterocysts and no akinetes. Planktothrix are unique because they have trichomes and contain gas vacuoles unlike typical planktonic organisms. Previously, some species of the taxon were grouped within the genus Oscillatoria, but recent work has defined Planktothrix as its own genus. A tremendous body of work on Planktothrix ecology and physiology has been done by Anthony E. Walsby, and the 55.6 kb microcystin synthetase gene which gives these organisms the ability to synthesize toxins has been sequenced. P. agardhii is an example of a type species of the genus. P. agardhii and P. rubescens are commonly observed in lakes of the Northern Hemisphere where they are known producers of potent hepatotoxins called microcystins.
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 1-2µm 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. Unlike many other cyanobacteria, the genome of A. thalassa does not contain genes for RuBisCO, photosystem II, or the TCA cycle. Consequently, A. thalassa lacks the ability to fix carbon via photosynthesis. Some genes specific to the cyanobacteria group are also absent from the A. thalassa genome despite being an evolutionary descendant of this group. With the inability to fix their own carbon, A. thalassa are obligate symbionts that have been found within photosynthetic picoeukaryote algae. Most notably, the UCYN-A2 sublineage has been observed as an endosymbiont in the alga Braarudosphaera bigelowii with a minimum of 1-2 endosymbionts per host. A. thalassa fixes nitrogen for the algae, while the algae provide carbon for A. thalassa through photosynthesis. There are many sublineages of A. thalassa that are distributed across a wide range of marine environments and host organisms. It appears that some sublineages of A. thalassa have a preference for oligotrophic ocean waters while other sublineages prefer coastal waters. Much is still unknown about all of A. thalassa's hosts and host preferences.
Nostoc punctiforme is a species of filamentous cyanobacterium. Under non-limiting nutritional environmental conditions, its filaments are composed of photosynthetic vegetative cells; upon nutrient limitation, some of these cells undergo differentiation into heterocysts, akinetes or hormogonia.
Cyanothece is a genus of unicellular, diazotrophic, oxygenic photosynthesizing cyanobacteria.
Gloeotrichia is a large (~2 mm) colonial genus of Cyanobacteria, belonging to the order Nostocales. The name Gloeotrichia is derived from its appearance of filamentous body with mucilage matrix. Found in lakes across the globe, gloeotrichia are notable for the important roles that they play in the nitrogen and phosphorus cycles. Gloeotrichia are also a species of concern for lake managers, as they have been shown to push lakes towards eutrophication and produce deadly toxins.
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.
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.
Aphanizomenon ovalisporum is a filamentous cyanobacteria present in many algal blooms.