Without bases for nucleic acids and amino

microorganism life would simply not exist. They are responsible for the oxygen
we breathe, providing the nutrients for the food we eat and even digesting that
food. The beneficial effects or microorganisms stems from their metabolic
activities in the environment. The substances that make up living material
consist on mainly Carbon, Nitrogen, Hydrogen and Oxygen. Without these
substances, life would cease to exist. Microorganisms have the ability to
recycle these primary elements making them available for other organisms such
as plants and animals. (Todar, K, 2012)

play a huge part in the Nitrogen cycle. All living organisms require Nitrogen
to synthesize protein and nucleic acids. Although the air we breath is almost
80% nitrogen, plants and animals are unable to use it in this form as it is
very unreactive. Plants require a ‘fixed’ source of nitrogen such as ammonium
ions or nitrate ions so that plants can absorb it. Nitrogen-fixing bacteria
such as Rhizobium, which lives in the root nodules of plants such as peas, are
able to reduce nitrogen gas to ammonium ions. The bacteria have a mutualistic
relationship with the plant, the bacteria provides the plant with a fixed
nitrogen source and receives carbon compounds such as glucose in return. The
nodules of the plants contain proteins such as leghaemoglobin which absorb
oxygen maintaining anaerobic conditions. Under these conditions the bacteria
use the enzyme nitrogen reductase to reduce the gas to ammonium ions. (Sochacki, F,

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next step in the cycle is the nitrification process. This process is undertaken
by chemoautotrophic bacteria that live in the soil. Chemoautotrophic bacteria
such as Nitrosomonas bacteria obtain their energy through oxidising ammonium
ions to nitrites. Nitrobacter bacteria are also chemoautotrophs but they obtain
their energy from oxidising nitrites to nitrates. This oxidation process
requires oxygen meaning that this process can only take place in well aerated
soil. Nitrates are then absorbed from the soil by the plants and used to make
nucleotide bases for nucleic acids and amino acids for proteins. (Sochacki, F,
2008) This allows the plants to grow and this provides a food source
for organisms such as herbivorous animals. The final part of the nitrogen cycle
is denitrification. Bacteria convert nitrates back to nitrogen gas, this occurs
when the bacteria involved are growing under anaerobic conditions such as
waterlogged soils. The bacteria use nitrates as a source of oxygen for their
respiration and produce nitrogen gas and nitrous oxide. (Sochacki, F, 2008)

atoms are cycled between the biotic and abiotic components of an ecosystem.
Microorganisms such as bacteria and fungi are decomposers that break down dead
and waste organic material. Without this process nitrogen and other valuable
nutrients would be trapped in the waste material and unavailable for other
organisms to use. Bacteria and fungi are saprotrophs, meaning they feed
saprotrophically. (Sochacki, F, 2008) Saprotrophs secrete and release enzymes
such as lipase and protease onto the waste material which breaks the material
down realising the nitrogen they contain as ammonia. This process is known as
ammonification. (Hopson, J, Postlethwait, J,  2006)

such as cyanobacteria play a huge part in CO2 fixation, this is the process
that makes organic carbon available for synthesis of cell material. This
process involves photosynthetic organisms which use the CO2 in the atmosphere
and covert it into organic material. Cyanobacteria and planktonic algae account
for nearly half of the primary production on the planet. Synechococcus, a
cyanobacterium, is a primary component of marine and fresh water plankton. This
unicellular prokaryote is involved in nitrogen fixation and oxygenic
photosynthesis, meaning that it plays a key role in recycling carbon, nitrogen
and oxygen. (Todar, K, 2012)

Microorganisms are also harnessed by humans to remove
pollutants from our sewage. If we were unable to do this the affects would be
devastating, absence of a sewage treatment system would could disastrous damage
to the environment. There are three stages to sewage treatment and
microorganisms play a large part in the process. The primary stage of the
treatment is first, this stage includes the physical seperation of sewage into
solids and liquids using a settling basin. The liquid sewage is then
transferred to the secondry stage of the process. In this stage microorganisms
are used to remove dissolved biological compounds. (Wagner, M, 1996) This type of microorganism requires oxygen as it
has an aeroic metabolism. The final stage of the process, the teriary stage
involves the disinfection of sewage. This section of the treatment requires
anaeronic microorganisms. Due to the nature of the microorganisms that are used
in the proccess multiple factors must be controlled to ensure the process is as
efficient as possible. Oxygen levels are closely monitored and controlled in
the secondry and tertiary stages of the process as oxygen is required as a
terminal electron acceptor in the degradation of organic matter. For example
the nitrification by Nitrosomonas and Nitrobacter species requires dissolved
oxygen to occur. Ph is also highly monitored as extremely high or low levels can
kill bacteria. The Ph of sewage is maintained at 7. (Hurwiz, E, 1960) Without microorganism sewage management would be
unable to take place and harmful pollutants would have a severe impact of the
environmet and wildlife.

In conclusion, without microorganisms life would simply not
exist. They provide us with the oxygen to breath, nitrogen in the soils to
grown plants, break down waste materials that trap nitrogen and other nutrients
and even allow us to digest the food we eat. The existance of microorgansims is
the only reason life as we know it exists on this planet.