Cyanobacteria (Essay Sample)

Cyanobacteria
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Essay Outline
* Introduction: A description of cyanobacteria including their structure and classification
* Environment: The different types of ecosystems where cyanobacteria exist
* Selection Pressures and Adaptations
* A discussion of the environmental pressures
* And how the cyanobacteria have been adapted to survive in such environments
* Conclusion
Introduction
Cyanobacteria also known as the Blue Green Algae are different from other kinds of bacteria since they posses chlorophyll a, which other photosynthetic bacteria don’t. Although they are referred to as algae, this is incorrect as algae are normally eukaryotic and the cyanobacteria are prokaryotic. The Blue Green Algae gets its name from a similarly colored pigment which is brought about by a combination of chlorophyll a and phycocyanin. Cyanobacteria belong to kingdom Monera in division Cyanophyta. In terms of cellular organization, the Blue Green Algae are prokaryotic and have a haploid lifecycle. They also reproduce through fission and their cell walls lack cellulose. However, unlike higher plants, in terms of chromosomal arrangement, the DNA of cyanobacteria are not attached or linked to histone proteins (Choudhary 171).
It has been argued that cyanobacteria play a key role in sustaining life; that the Blue Green Algae created the oxygen in our atmosphere during the Proterozoic Era and that the chemical composition of the atmosphere was quite different from what we have and it couldn’t sustain life. It is known that the cyanobacteria produce oxygen as a by-product of photosynthesis and they are thought to have formed the conditions in the previous atmosphere that stimulated evolution of eukaryotic photosynthesis and aerobic metabolism.
Environment
The cyanobacteria can survive in a wide range of habitats including lava flows, frozen lakes, deserts and acidic marshes or bogs. However, they are frequently found in aquatic environments that are alkaline and also those that have different ranges of acidity and salinity. Cyanobacteria can also survive in the atmosphere, the rocks or soil. Cyanobacteria are able to exist in all these kinds of environment because they very genetically diverse. They also have quite a number of unique adaptations that enable them to survive or exist in all these different kinds of environments.
Besides the wide range of ecosystems that they can occupy, cyanobacteria can also exist in a wide variety of organizations including colonial, filamentous and unicellular. The fact that cyanobacteria can occupy very extreme environments often means that they are usually the primary colonizers of such environments. As members of a cell colony they are usually not differentiated from each other. The filamentous organization occurs when the cyanobacteria form a cells chain complete with an enveloping sheath (Chauhan and Varma 22).
Selection pressures and Adaptations
The majority of cyanobacteria are photoautotrophic meaning that they fix Carbon IV Oxide (CO2) and release oxygen. The fact that they need CO2 to survive made them acquire an adaptation referred to as CO2 concentrating mechanism (CCM) to enable them to survive in low Carbon IV Oxide environments. The CCM actively transfers and builds up inorganic carbon within the cell. This creates a high concentration carbon IV oxide pool around ribulose bisphosphate caroxylase-oxygenase (RuBisCO) which is a Carbon IV Oxide fixing enzyme. RuBisCO helps convert CO2 into sugars.
One of the other important adaptations of the cyanobacteria is its ability to fix gaseous nitrogen which enables them not to rely on any other combined source of nitrogen. Cyanobacteria have nitrogenase – an enzyme complex that is fixes elemental nitrogen. When cyanobacteria are in low nitrogen environments they produce heterocysts. Heterocysts are cyanobacteria cells that are not only larger than normal but also thicker; this makes them better at fixing nitrogen. The fact that cyanobacteria can fix nitrogen has made them a very useful agricultural tool. For example, the cyanobac...