Cyanobacteria refer to a phylum or group of micro-organic bacteria that obtain their foods and energy through photosynthesis. It is believed that cyanobacteria helped in formation and conversion of the earth’s atmosphere into ozone layer through their ability to synthesize food using sunlight and oxygen. According to Whilton, cyanobacteria are capable of carrying out oxygenic photosynthesis and hence created a balance of the amount of oxygen in the atmosphere (117). Consequently, these photosynthetic activities of cyanobacteria led to drastic changes in the composition of the earth’s atmosphere. Fossil scientists believed that these photosynthetic activities of cyanobacteria resulted into increased emission and supply of oxygen into the earth’s atmosphere. This also consequently led to extinction of numerous anaerobic organisms which could not tolerate the presence of high levels of oxygen in the atmosphere.
Oxygenic photosynthesis is the ability of organisms, usually aquatic microorganisms, to extract oxygen from water and use it during photosynthesis. In this case, water acts as the electron donor for oxygen atoms.
Ecology of Cyanobacteria
Most cyanobacteria are found in damp places as well as in water bodies, usually on rocks surfaces. Aquatic cyanobacteria are often found in both fresh water bodies like rivers and lakes and in marine environments such as ocean and seas. Moreover, traces of cyanobacteria have been found in inlands, especially on damp soils and rock surfaces. According to Whilton, plank-tonic cells of cyanobacteria have also been found in desert places on moistened surfaces of rocks (92).
Cyanobacteria also occur in form of blue-green scum on water body surfaces. The blue-green colors of most cyanobacteria have earned them the name blue-green algae. Some biological scientists also refer to them as blue-green bacteria. Garcia Flores proposes that the name “blue-green algae” was developed from cyanobacteria’s ability to photosynthesis food in aquatic environments. Flores asserts that almost all cyanobacteria are aquatic in nature and thus live in water bodies (38).
Characteristics of Cyanobacteria
Cyanobacteria consist of a group of unicellular and colonial organisms. The colonial species of cyanobacteria usually form larger filaments that are referred to as trichomes. Trichomes can be further differentiated into a number of cells such as photosynthetic, body and vegetative cells. All cyanobacteria have the ability to manufacture own foods.
Cyanobacteria are very tiny and small and hence cannot be seen easily with the naked eyes. However, they sometimes grow into groups called colonies which might be large to notice and observe. Cyanobacteria form the largest number of photosynthetic microorganisms. According to Flores, the bodies of cyanobacteria are greatly varied both in shape and appearance (61). Their body diameters measure approximately five microns. Although Cyanobacteria resemble eukaryotes, they are true prokaryotes.
Cyanobacteria have the capability to live in anoxic environments. This characteristic greatly differentiates them from other forms of bacteria. Anoxic environments are environments with no oxygen supply.
History of Cyanobacteria
Cyanobacteria are believed to be one of the oldest living organisms whose fossils have been found on earth. Historical scientists believed that most of their fossils are as old as four billions years. Surprisingly, they still exist upto date.
Importance of Cyanobacteria
The major importance of cyanobacteria has been generation and supply of oxygen into the earth’s atmosphere. Through photosynthetic activities, cyanobacteria have been able to maintain a suitable balance on the amount of oxygen in the atmosphere. It is estimated that cyanobacteria supplies nearly twenty five percent of the earth’s atmospheric oxygen.
Whilton argues that cyanobacteria are one of the most important forms of bacteria found on the earth’s surface (183). Mineralogists have linked various deposits of oil in submarine water bodies to ancient activities of cyanobacteria. It is belied that cyanobacteria were responsible for oxidation of minerals thousands of years ago.
Through increased supply of oxygen into the atmosphere, cyanobacteria help in reducing the amounts of greenhouse gases such as carbon dioxide and methane available in atmospheric layers. Cyanobacteria can also be used in manufacturing nitrogen fertilizers that are used for various agricultural activities such as growing of food crops like maize and beans.
Additionally, Flores also suggests that most plants have cyanobacteria in their chlorophyll cells. Cyanobacteria are thus used by plants in manufacturing foods. She asserts that this endosymbiosic relationship between plants and cyanobacteria have been observed in late Proterozoic era where eukaryotic plants host cyanobacteria which would manufacture foods for the plants in exchange of habitation (156-157).
Through their ability to manufacture own foods, cyanobacteria form the most important basis for food chain in aquatic environments. Other living organisms such as aquatic plants and animals depend on cyanobacteria for food and supply of oxygen in the water bodies.
Formation of Stromatolites by Cyanobacteria
Cyanobacteria have tiny pigments in their bodies that are water soluble. These pigments are used by the microorganisms in formation of chloroplasts. Chloroplasts form an integral component of plants that are used during photosynthesis. During the process of photosynthesis, cyanobacteria form layers of thin mass-like structures on surfaces of shallow water bodies. The cyanobacteria trap, precipitate and bind together various layers of granule particles to form stromatolites. Gaspar describes that stromatolites form when cyanobacteria group themselves together into colonies (184). These cyanobacteria colonies are often formed on rock surfaces or shallow parts of the water. This thus explains the existence of many stromatolites on shallow parts of water bodies, for example the shores of oceans and along river banks. The stromatolites are deposits of calcium carbonates formed from colonies of cyanobacteria.