Blue-Green Algae (Cyanobacteria)

Historical Perspective

In the Bible, it was recorded that Moses, the prophet, took his people across the river Nile, when he strived for the liberation of the Israelites from the slavery in Egypt, and it turned to blood, since then, there have been other cases of rivers turning to blood, or at least what appears to be blood, for instance, the China’s largest river, Yangtze, was reported to turn red last September (Daily mail). Several theories were put forward in an attempt to explain the occurrence. They varied from dyes to industrial effluents, but one theory stood out for its simplicity and logic, several marine biologists suspected that it was not an outstanding wonder of the world, it was just some small organisms coming out to play in the sun; those organisms were algae. As a rule, when small organic bodies of water, whether natural or manmade, are left unattended, one can notice a layer of a blue-greenish scum in the water. That change in color of the water is due to the presence of cyanobacteria.

Cyanobacteria are the bacteria of the class photo-bacteria, grouped in the subsection 1 of the Bergey’s Manual of Systematic Bacteriology. They are a substantially ancient group of living organisms, whose earliest records can be found in the Archean rocks in Australia. These fossils are approximately 3.8 billion years old. They are said to be the earliest forms of life known; thus, scientific historians proposed that the oxygen in the atmosphere is the result of the activity of tons of cyanobacteria that were actively respiring in the Proterozoic and Archean ages. Predominantly, they all belong to the genus Nostoc, which is usually found in nature such as free living plants (Falcon). In most places, where cyanobacteria occur in nature, they are the initial colonists (this means that they are the first organisms to live in or on any given place or environment) and are especially resilient as evidenced by the range of territory they have been discovering to live in, which range from beneath 5m of ice, to hot springs and under rocks in the desert.

Cyanobacteria are a group of simple, single celled autotrophic prokaryotes that contain specific pigments that allow them to photosynthesize their food. These pigments are the green pigment chlorophyll, which all green plants contain and which enables them to synthesize food from the sun and the blue pigment, Phycobillin. These two pigments gave them their names – the blue-green algae (Britannica). The genus Nostoc generally refers to non-motile plants, but it is able to infect other plants by means of a motile filament, known as hormogonia, which is unique to them as it serves as a means of dispersal for them, as well.

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Phylogenetic Classification of the Organism and Morphology

In terms of morphology, they are devoid of many of the organelles of typical bacteria, like a nucleus and chromosomes, inside their cell; however, they have peptidoglycans in their membranes. They share further similarities with bacteria like their method of locomotion, as well as the gliding movement, prompting biologists to label them as a subgroup of the gram negative bacteria class. A number of these organisms usually have a small bubble of air, which keeps them floating in the water, and is exposed to the sun, which they need to synthesize their food. In general, most blue-green algae or cyanobacteria are unable to synthesize their food in the absence of sunlight. They possess several pigments: blue, green, red, yellow, violet and deep blue. They can be filamentous or coccoid.

The coccoid variants are usually the phytoplankton that abound in the middle of tropical oceans and are a highly significant part of the base of the aquatic food chain. Moreover, they are at the top of the energy triangle because of their unique ability to harness the sun’s energy and bring it into the sea’s ecosystem. The filamentous algae usually form chains or mats and are found together with other organisms in symbiotic relationships like ferns, diatoms, lichens and mosses. When the climate becomes unfavorable, these organisms form cysts that tide them over till, when conditions improve (Florida). On the land, however, they are of paramount significance as they are one of the unique groups of organisms that provide a substantially vital nutrient for plants, namely nitrogen. This is because they are able to convert the atmospheric nitrogen into a form that is readily accessible to the roots of leguminous plants, in a process known as the nitrogen fixation. This is a crucial part of the nitrogen cycle. In the rice paddies of Asia, it is not an uncommon practice to find the fern Azolla floating among the plants. This fern coexists with Anabaena, a cyanobacterium in its leaves. The relationship provides the rice farmer with a cheap source of nitrogen, which would otherwise be bought (Berkeley).

However, the group of these bacteria that are of the most significance to a man are the plankton form of it that floats in water bodies, especially when there is a green scum. For years, they have been recognized as a cause of disease in humans, but in 1989, they scientists attributed them a specific significance after two rather peculiar events: in Rutland, dogs and sheep were reported dead after a bloom in one of the water bodies, and army cadets were reported with respiratory diseases after canoeing in the Rudyard Lake. It resulted in a report (National River Authority)

Cyanobacteria reproduce asexually by multiple or binary fusion, when they live in the unicellular coccoid form or by spore formation and fragmentation, when they live in colonies or the filamentous form. When conditions are perfect, they can have explosive growth. This growth is what is known as the bloom. It typically occurs when the water body has been polluted by nitrogenous or phosphorous waste. This particular etiology of blooming is especially dangerous, because the bloom is capable of such exponential growth that the oxygen supply of the lake, river or water body can be completely used up to such an extent that fish and other aquatic animals in the water body can die off completely (Havens, n.d.). The conditions synonymous with blooms include light intensity gas vacuoles, nutrients levels, growth rate and temperature among others (Mur, Skulberg, & Utkilen).

Properties of The Organism That Make It Beneficial to The Ecosystem in Which It Lives

Harmful algal blooms (HABs) damage the aesthetic properties of water bodies and make the water unsuitable for human activities, especially in the warm months. Several algae are known to have toxins that can be dangerous to aquatic life (CDC).

Cyanobacteria are known to produce several toxins, which are highly lethal. In fact, they form some of the most lethal substances known, for instance, the lethal dose for a man of Microcystin is 50ug/kg juxtaposed. This with a lethal dose of the more popular poison, sodium cyanide 10000 ug/kg, and one begins to get an idea of how lethal these toxins can be. Toxins, like Microcystin, are among the major causes of fatalities in animals as well as potentially humans; the toxins, which are of a peptide nature produced by cyanobacteria, have been shown to cause a weakness, vomiting, pilo-erection, diarrhea and coldness of the extremities. They can be fatal in 2 to 24hrs, depending on the concentration of the toxin imbibed by the organism in question. The research has shown that their toxins have their primary effect on the internal organs like the liver. It has also proved to be the cause of thrombosis of the pulmonary vein, and some rather potent neurotoxins have been shown to be produced by cyanobacteria. For example, Anatoxin-a is a neurotoxin produced by the fern Anabaena flos aquae, it is a cocaine analogue, and fatalities have been reported in experimental animals after the exposure for 5-30minutes due to the paralysis of the respiratory system. The neurotoxin neosaxitoxin is produced by Aphanizomenon flos aquae; it has been shown to cause paralysis by obstructing the flow of sodium in neurons. Several other toxins have been known to be promoters of the tumor growth in experimental animals (JMM).

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The consumption of cyanobacteria in water contaminated with algal blooms, eating fish that have been caught in reservoirs that contain these algae as well as contact with such water bodies are the direct cause of several human conditions, which range from allergic rhinitis, conjunctivitis or dermatitis. A rather painful diarrhea was reported by a physician after the accidental immersion in a contaminated lake; in the report the physician was said to pass out feces that contained the organism Anabaena and Microcystitis. The feces were described as green and slimy (Dillinberg & Dehnel). The army recruits that were earlier mentioned were admitted to a medical facility with a sore throat, blistering around the mouth, basal pneumonia and vomiting, whereas the water body they canoed in was shown to be infested with Micro Cystitis.

In the aborigine community in Australia, there was reported a severe malaise that was linked to a cyanobacteria infested water body. The illness was presented with acute hepatitis, anorexia, hepatomegaly and vomiting in addition to acidosis, the serum electrolyte imbalance and hypokalemia; all of them recovered in less than a month (Byth)

HABs Formation and the Toxigenic Properties of Blue-Green Algae

It has been shown that some of the neurotoxins are relatively labile and without any external factors and can be turned into non-toxic products, but those of the cyclic-peptide nature are rather stable and are the result of their chemical structure. In their skeleton, they are composed of several amino acids so unusual that there are few organisms that actually contain the enzymes required to break them down. In a study of hepatotoxins on Lake Michigan, it was found out that the toxin produced by Microcystin was substantially peculiar in its dried form as it proved to retain its high toxicity even 6 months after drying as it was preserved by the encapsulation inside dried cells, thus, evading the degradation (Ressom).

Global Epidemiological Report/Data

In the US, the data on the detection of directly cyanobacteria related illnesses are not immediately available, but several reports have shown that cyanobacteria in the form of bodies have been detected in the stools of people, who have had syndromes of fatigue vomiting and diarrhea for extended periods, each of these cases reported were those of immune-compromised patients or patients that had recently visited tropical countries. The last documented case of CLBs occurred in a hospital in Chicago on the 9th of July, 1990. It was reported in the infectious disease department that several staff physicians reported with diarrhea and with mild fever for one day, followed soon after by episodes of the explosive diarrhea, severe abdominal cramping, occasional vomiting, nausea and anorexia. The diarrhea was in remission for the next few couple of days, but cyclically relapsed for the next few weeks, and in each of the relapses, the reported symptoms were similar to the first one in addition to occasional constipation. All of the feces collected during this period from the sick people were bacteriologically tested and proved negative for the causative agents of other possible abdominal conditions like Yersinia, Vibrio Cholera, Shigella, Salmonella and Campylobacter, nor were parasites or their ova found. The Acid fast staining and microscopy of the samples revealed that CLBs were present in them (MMWR)

The majority of data on effects of Cyanobacterial toxins are based largely on the findings from animals both domestic and wild. As it has been recorded, the majority of the effects are: hepatotoxic, neurotoxic, with associated disturbances of the respiratory and gastroenterological systems, allergic and dermatologic reactions are consistent with the exposure to cyanobacteria and their toxins. People that have swum in lakes and water bodies that have these algae blooms habitually report various allergic reactions, which include conjunctivitis, contact dermatitis and a hay fever like condition (Backer). In Australia and New South Wales, a study was carried out that researched the exposure to the Cyanobacterial occurrence and cell concentration in sources of drinking water in the first third of pregnancy and found a significant disparity in birth weight of infants. The study was not conclusive enough to surmise a chain of causality, linking the two, but it suggested that there might be something in that system that could link both of them (Pilotto).

Several toxins have been shown to be produced by cyanobacteria; they include Microcystins, Nodularins, Anatoxins, Saxitoxins, Cylindrospermins, lyngbyatoxin-a and Aplysiatoxins respectively. These toxins are generally released by the organisms into their environment, and they usually cause a smell or taste that damages the organoleptic quality of water bodies; as a result, humans will rarely drink from such contaminated bodies of water, but animals, on the other hand, on hot days in particularly cannot be prevented from drinking such water as they are not put off by the taste or smell as humans are. However, humans imbibe these toxins through recreational and drinking water supplies. The fact is that the absence of scum on the water surface does not preclude the presence of the organisms or their toxins. Typically, these toxins are only released from these organisms at the old age or death as a result water that may be free of the algae may not be free from the toxins that were released into the water at the death of the organism. Humans might come into contact with these organisms by taking them up in the course of water based recreation or by drinking the water that contains the organism and its toxins. The use for gardening or agriculture of contaminated water is another possible route; in dialysis, there is a possibility of the patient’s treatment water being algae contaminated (Hindma).

Effects of Toxicosis and The Symptoms of Toxicosis

Anatoxin-a, is a neurotoxin produced by about 8 genera of cyanobacteria, including Anabaena Spp. It is known as the very fast death factor; moreover, it is a lethally potent cholinergic agonist, the mechanism of action is by blocking the transfer of acetyl-choline (a neuromuscular transmitter) across the neuro-muscular junction. It is usually lethal within minutes, although this effect depends on the dose of the toxin consumed and the emptiness of the stomach. Clinical signs of neurotoxicosis include a progressively decreased movement, collapse, muscle fasciculation (twitching), pronounced abdominal respiration, convulsion, cyanosis and eventually death (Carmichael, Yu, He, He, &Yu) The death has been suggested to result from the respiratory paralysis due to Anatoxin-a induced neurotoxicosis.

It has also been suggested that the lipopolysaccharides (LPS) in the walls of the cyanobacteria possess toxic properties. Nonetheless, no clear scientific evidence that supports that theory has been published; while there may exist the capacity to elicit certain reactions from host cells, no study has shown these compounds to elicit this reaction in the absence of other virulence factors. However, in the presence of other factors, they have been shown to be capable of eliciting emesis, which is one of the gastroenterological symptoms associated with the exposure to toxins. Furthermore, no evidence exists that shows the ability to independently elicit a cutaneous reaction by LPS (Stewart, Schluter & Shaw).

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People have been known to consume algae as dietary supplements. Of all the algae used, Spirulina Spp is the most popular plant among those that are sold as dietary supplements. It has considerably old origins; in this respect, it has been known to be eaten by the Aztecs, then it was known as Tecuitatl, and in the 9th century in Chad, it was made into small cakes known as “dihe”. Today, several companies produce and market these algae as a healthy dietary supplement. Spirulina as a food source was popularized by NASA, after they employed it as a dietary supplement for their astronauts as they embarked on missions. It possesses immuno-modulatory properties as well as has anti-inflammatory effects. It achieves this by suppressing the mast cells ability to release the inflammatory modulator histamine (Karkos, Leong).

It has been shown to be a substantially effective food source and has even gained the FAO recommendation as a potential food source. It has been proven that it possesses significant antioxidant properties; a chromophore bound to its chief protein has the potential to inhibit NADPH oxidase. This chromophore is known as Phycocyanobilin (PCB). Its action mirrors that of free bilirubin in the body. The intake of this has been shown to have a potential to prevent vascular problems that range from heart failure to hypertension as well as cancers, complications from diabetes, neurodegenerative and disorders of an inflammatory nature. Due to the central neuro-protective effects, it is suspected that this compound has the capacity to cross the blood brain barrier (Ali & Saleh).

Beneficial properties of blue green algae as a source of food, and possibility of derivation of chemotherapeutic products from them. Avenues for further research.

The aquatic ecosystem, like every other ecosystem, depends exclusively on the sun to provide the initial energy that can be harnessed to provide food for the living things in that system. At the top of the pile of the energy converter in the microscopic blue-green algae, it harnesses the sun’s power to feed the seas, oceans and lakes. In the summer months, when the temperature, wind and nutrients are perfect, they undergo an explosive growth and form a scum or bloom that is billions of cells thick for a few weeks, till they are consumed or die off. These blooms can be unsightly and give off a rather unpleasant smell; they also impart an unpalatable flavor to water, in which they are found. In addition to this, some of them produced various toxins, which can be lethal in the right dose. As a rule, their lethal effects are limited to animals, but on occasion humans that come in contact with these contaminated water come down with various ailments. Now, it is pertinent to note that not all cyanobacteria are toxigenic, but it is better to err on the side of caution.

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Whereas it possesses a significant health hazard, every state in the US has a public safety department that oversees the water bodies within its borders, while several of them outline on what to do in case of the suspected exposure to these organisms or their toxins. Generally, people are warned against swimming in waters that are showing blooms or even eating fish caught in such waters without cleaning them properly. Although no significantly large outbreaks have been reported from the exposure to the organisms, several cases or symptoms of the irritation have resulted from the exposure to them. In some cases, they have been linked with neuro degenerative disorders. (Holtcamp)


The cyanobacteria are an interesting group of bacteria; therefore, a lot of research regarding their possible use in therapy of various diseases, like HIV and cancer, are currently ongoing and showing promise (Darkos et al., 2011). They have also shown to have some prophylactic potential, as well as the possibility that they could possess antibacterial properties, which could be harnessed in the future.

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