''Cylindrospermopsis raciborskii'' is a
freshwater cyanobacterium
Cyanobacteria (), also known as 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, blu ...
.
Introduction
This bacterium is an aquatic photosynthetic bacteria belonging to the phylum
Cyanobacteria. They are composed of chained filaments known as
trichome
Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a p ...
s that can show variation in
morphology
Morphology, from the Greek and meaning "study of shape", may refer to:
Disciplines
* Morphology (archaeology), study of the shapes or forms of artifacts
* Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
, varying from about 50–300 micrometers in length.
These bacteria can also produce a thick walled, cylindrical, spore like structure known as
akinete
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 sto ...
s, which also demonstrate variation in morphology. Some strains of this species are able to produce several toxins which affect humans:
cylindrospermopsin
Cylindrospermopsin (abbreviated to CYN, or CYL) 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 ...
,
anatoxin-a
Anatoxin-a, also known as Very Fast Death Factor (VFDF), is a secondary, bicyclic amine alkaloid and cyanotoxin with acute neurotoxicity. It was first discovered in the early 1960s in Canada, and was isolated in 1972. The toxin is produced by mu ...
and
saxitoxin
Saxitoxin (STX) is a potent neurotoxin and the best-known paralytic shellfish toxin (PST). Ingestion of saxitoxin by humans, usually by consumption of shellfish contaminated by toxic algal blooms, is responsible for the illness known as paralyt ...
.
This first toxin, cylindrospermopsin, has the ability to affect the liver and kidneys in humans as well as cause mild skin reactions upon exposure.
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
Butylated hydroxytoluene (BHT), also known as dibutylhydroxytoluene, is a lipophilic organic compound, chemically a derivative of phenol, that is useful for its antioxidant properties. BHT is widely used to prevent free radical-mediated oxidat ...
, an antioxidant, food additive, and industrial chemical.
Phylogeny
Domain – Bacteria
The Tree of Life contains three Domains:
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
,
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
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 pigment
A photosynthetic pigment (accessory pigment; chloroplast pigment; antenna pigment) is a pigment that is present in chloroplasts or photosynthetic bacteria and captures the light energy necessary for photosynthesis.
List of photosynthetic pigme ...
s in their
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...
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
''Cylindrospermum'' is a genus of filamentous cyanobacteria found in terrestrial and aquatic environments. In terrestrial ecosystems, ''Cylindrospermum'' is found in soils, and in aquatic ones, it commonly grows as part of the periphyton
Per ...
'' is found in soils, while in aquatic it commonly grows as part of the
periphyton
Periphyton is a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in most aquatic ecosystems. The related term Aufwuchs (German "surface growth" or "overgrowth") refers to the col ...
on aquatic plants. The particular genus is a heterocystous (
nitrogen-fixing
Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atm ...
) cyanobacterium.
:
Species – ''Cylindrospermopsis raciborskii''
Ecology
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
The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lak ...
located in North America.
The bacterium has the ability to fix atmospheric nitrogen as well as absorb and store phosphorus.
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.
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
Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers, the Epilimnion comprising the top warm layer, the thermocline (or Metalimnion): ...
; increased retention time; high pH; high sulfate concentration;
anoxia in at least some strata; high turbidity; high incident irradiation; and low
macrophyte biomass.
History
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.
The strain found in North America is thought to have originated in South America and it is believed that
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
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.
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
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
in Florida, as well as toxicity to some
shellfish, which it accumulates in organisms such as
crawfish.
Nitrogen-fixation pathway
''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
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 fr ...
. It provides the cells in the filament with nitrogen for biosynthesis by fixing nitrogen from dinitrogen (N2) using the enzyme
nitrogenase
Nitrogenases are enzymes () that are produced by certain bacteria, such as cyanobacteria (blue-green bacteria) and rhizobacteria. These enzymes are responsible for the reduction of nitrogen (N2) to ammonia (NH3). Nitrogenases are the only fa ...
. 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:
* Producing three additional cell walls, including one of
glycolipid that forms a hydrophobic barrier to oxygen
* producing nitrogenase and other proteins involved in nitrogen fixation
* the degradation of photosystem II, which produces oxygen
* up-regulation of glycolytic enzymes
* producing proteins that scavenge any remaining oxygen
* containing polar plugs composed of cyanophycin which slows down cell-to-cell diffusion
''Cylindrospermopsis raciborskii'' obtains its fixed carbon via
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
. The lack of photosystem II would normally prevent it from photosynthesizing, but the vegetative cells provide the necessary
carbohydrate
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or m ...
s, 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
Photosystem I (PSI, or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I is an integral membrane protein complex that us ...
, allowing it to generate
ATP by
cyclic photophosphorylation In the process of photosynthesis, the phosphorylation of ADP to form ATP using the energy of sunlight is called photophosphorylation. Cyclic photophosphorylation occurs in both aerobic and anaerobic conditions, driven by the main primary source of ...
.
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
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
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.
Pathogenesis
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. 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.
Population dynamics
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. 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.
Palm Island incident
In 1979, ''Cylindrospermopsis raciborskii'' was attributed with causing
hepatoenteritis (an infection of the liver resembling
hepatitis
Hepatitis is inflammation of the liver tissue. Some people or animals with hepatitis have no symptoms, whereas others develop yellow discoloration of the skin and whites of the eyes ( jaundice), poor appetite, vomiting, tiredness, abdominal ...
) in 148 people off the northern coast of Queensland at Palm Island.
The contamination of drinking water was attributed to
copper sulfate Copper sulfate may refer to:
* Copper(II) sulfate, CuSO4, a common compound used as a fungicide and herbicide
* Copper(I) sulfate
Copper(I) sulfate, also known as cuprous sulfate, is an inorganic compound with the chemical formula Cu2 SO4. It ...
treatment in the island's drinking-water supply,
Solomon Dam
Solomon Dam is the main source of fresh water on Great Palm Island, Queensland, along with Francis Creek Dam.
See also
*List of dams and reservoirs in Australia
Dams and reservoirs in Australia is a link page for any dam or reservoir in ...
. The copper sulfate was intended to control a dense
algal bloom
An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term ''algae'' encompass ...
. 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
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
.
See also
*
Butylated hydroxytoluene
Butylated hydroxytoluene (BHT), also known as dibutylhydroxytoluene, is a lipophilic organic compound, chemically a derivative of phenol, that is useful for its antioxidant properties. BHT is widely used to prevent free radical-mediated oxidat ...
*
Cyanotoxin
Cyanotoxins are toxins produced by cyanobacteria (also known as blue-green algae). Cyanobacteria are found almost everywhere, but particularly in lakes and in the ocean where, under high concentration of phosphorus conditions, they reproduce exp ...
References
{{Taxonbar, from=Q5199329
Nostocales