Student name: sa354
Essay title: How would you convince a
friend that microorganisms are more than
just disease causing agents?
Student name: sa354
Module: Microbiology
Lecturers: Dr. Shaun Heaphy & Dr. Martha Clokie
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Student name: sa354
Have you ever wondered how life would be without microorganisms?
The answer is really simple if you consider that human body is full of different
microorganisms each specified for a certain function. Most of the people believe
that all microbes are pathogens causing diseases and lead the infected host to
death.
People have this opinion due to the huge increase of serious diseases like
Aids and Hepatitis B, which are caused by specific viruses and lead millions of
people to death. In addition, there are many infectious microorganisms that
cause serious problems for example in mouth cavity. These are anaerobic
bacteria that form spores by enclosing themselves in capsules and absorb
substances from their environment to survive. Many protozoa also cause serious
dental infections, while fungi cause dermatophyte and nail infections.
All these infections make people believe that all microorganisms are
disease-causing agents but this is not the whole truth. A high proportion of
microorganisms have a vital role in human body health conservation and at the
same time in life on earth. For example human mouth cavity is a whole
ecosystem for some bacteria, which some of them prefer life between teeth,
others live in the gums or in the roof of the mouth or even in the cracks on the
front and back of the tongue. These microorganisms are there to eat food that
becomes lodged in parts of our mouths and protect us from the invasion of bad
bacteria, viruses, protozoa and fungi. Furthermore, the results of a recent
research of scientists in Switzerland, published in "Science Daily (2008)"
showed that some anaerobic bacteria can create the distinctive flavours of
certain food. The way these bacteria function is by the production of food odors
from odorless components of food, allowing people to fully taste fruits and
vegetables. "The mouth acts as a reactor, adding another dimension to odor
perceptions", the scientists explained. That was a really interesting discovery
which shows that not only most of bacteria are not harmful but some of them
can actually improve taste in our mouth.
Furthermore, apart from the mouth cavity, bacteria are all over the
digestive system, in the large intestine and in the part of the small intestine
below the stomach. Some of these bacteria are: the Fusobacteria, the
Eubacteria, the Peptostreptococcus etc. These microorganisms are friendly to
humans because they provide protection against harmful bacteria that try to
invade the cells of the intestinal lumen. Human have so many benefits from
those and may even not know it. For example Bacteroides are essential to our
digestive system because they produce specific enzymes that break down
polysaccharides in the cell walls of plants when we eat them. If these bacteria
never existed in our intestine they would not produce their enzymes which are
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really important because they are the ones that release the nutritional value of
vegetables and other plant material. In addition, some other bacteria make
vitamin K, which is important for the functioning of some proteins involved in
blood clotting, others make group B vitamins which are difficult to be found
from food, some others have a fundamental role in stimulating the immune
system and others help in digesting drugs that are not more needed in the
organism. Moreover, another group of intestinal microorganisms is Probiotics,
which are friendly bacteria that defend the stomach and intestines from
infections of harmful bacteria as well as contribute in food digestion, so that we
can take the essential nutrients. Other benefits we get from these bacteria is that
some of them can decrease fungus diseases, improve lactose intolerance,
contribute in a lower cholesterol and can even prevent cancer. Generally
Probiotics are useful for the treatment of various gastrointestinal diseases. It is
now obvious that symbiosis with these bacteria is necessary for the
conserveation of our health. "... these 'probiotic bacteria can be beneficial in
other ways -- contributing to the health and balance of the intestinal tract and
helping fight illness and disease. Learning about the genetic makeup of
probiotic bacteria can help in the prevention and treatment of a variety of
gastrointestinal disorder (Osolin (2002) cited in Rubin)"
Bacteria are a protective mechanism against pathogen microorganisms
not only in internal cavities of the human body but also in external surfaces i.e.
the skin. These prevent pathogen bacteria to grow there by creating conditions
which do not allow their survival. For example Staphylococcus Epidermidis
(friendly) prevents the invasion of Staphylococcus Aureus (pathogen) in the skin
cells. In addition another bacterium, called Corvnebacterium xerosis lives on
the transparent layer that protects the cornea of the eye, in a high salt
concentration and eliminates any pathogenic species that may enter the eye.
However microorganisms are not only related to the human body
protection. Specific microorganisms have a huge contribution in drink and food
industry. Yogurt, bread, cheese, wine and beer production are some of the food
and drinks in which microorganisms involve. The process of their production is
called fermentation. By this process harmless microorganisms grow in food or
drink and spoilage causing microorganisms do not establish to grow.
Fermentation is a technique that requires certain ingredients and strictly
controlled conditions (temperature and pH). Microorganisms eat spoilagesensitive parts of the food and release chemicals as a by-product thus they
maintain in food preservation and flavour formation.
Let’s see what happens in bread fermentation. The most common starting
material is wheat or other cereal grains and the microorganism used is
Saccharomyces cerevisiae (yeast). Most profitable temperature is 30˚C and the
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pH is 4-5. The yeast is added to the dough, starts to digest sugars (found in the
dough) and produces ethanol and carbon dioxide or various acids and organic
compounds, through pyruvate metabolism. The carbon dioxide forms "bubbles",
which are trapped by the wheat gluten and this is what makes the bread to rise.
Ethanol is eliminated through baking and that is why bread contains no alcohol.
Finally, the yeast gives to dough its flavour.
The same process is followed in alcohol fermentation, where yeast is added to
crashed grapes and sugar is converted to ethanol under anaerobic conditions.
"The AFM is ideal fo rstudying enzymes and micro organisms for development
of the biomass to ethanol process (Halotec (2008) cited in Laumen)."
Cheese fermentation is more complicated. The process starts with milk
bacteria which break down lactose and through the process of glycolysis and
pyruvate metabolism produce lactic acid under anaerobic conditions. Then the
enzyme rennet is added and lactic acid acts with it to curdle the milk. Finally the
whey is drained off and the curds are compacted and then various microbes are
ripening into a mature cheese.
Apart from food and drink industry many microorganisms in land go
through the carbon cycle where they produce carbon dioxide through cellular
respiration so that other organisms, like chemoautotrophs, can take it and fix
organic compounds essential for their functions, because carbon is the main
building block of life. Bacteria and some fungi take part in chemical reactions
on the tissues of organic matter and convert the carbon containing compounds
into carbon dioxide and water or to methane. Methanogenesis happens only in
Archaea, which reduce carbon dioxide from the atmosphere, under anaerobic
conditions. The final electron acceptor is carbon while other electron acceptors
are reduced because of the hydrogen and carbon dioxide increase.
Methanogenesis plays a fundamental role in life because without it we would
have a huge production of unused carbon products. The bacteria that take part in
the carbon cycle help in the creation of fossil fuels. Dead bacteria and fungi
were buried under layers of sand with layers of organic matter on top of them
creating pressure. The remains of the organic matter were compressed and we
had the formation of carbon-rich fuels, natural gas and coal, which produce
huge amounts of energy when heated.
Moreover some bacteria are involved in nitrogen cycle, which describes
the cycle of nitrogen from the atmosphere to bacteria, animals and plants back
to the atmosphere. The reuse of nitrogen is really important for the survival of
living things. However sometimes nitrogen is locked in the bodies of dead
organisms, thus the cycle is not completed. This is when bacteria that fix
nitrogen from the air provide the essential supplies of nitrogen so that organisms
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can develop and survive. These bacteria live in the roots of plants and produce
nitrogen which is important to plants because is essential for protein formation,
thus plants produce fruits that have high amounts of protein, so that they do not
need high amounts of energy to obtain the necessary building blocks. Because
plants cannot obtain nitrogen from the air, these bacteria have developed
enzyme systems for nitrogen absorption and its conversion to nitrogen dioxide
or ammonia. These reactions happen without the presence of oxygen, which is
the best environment for the bacteria which are in the roots of plants. The roots
have lack of oxygen because of leghamoglobin, a plant protein that binds to any
oxygen atom as a result the decrease of oxygen concentration. Symbiosis with
these bacteria is beneficial because not only they produce extra nitrogen
supplies for the plants but also after the death of a plant the proteins are released
in the soil and become available to other plants. Moreover, they indirectly
contribute in the continuity of life. Bacteria which are already present in soil are
able to fix nitrogen from the air, called Cyanobacteria, which are also
responsible for the presence of oxygen in the atmosphere. Other bacteria such as
Azotobacter can fix nitrogen even under aerobic conditions.
More advantages are gained by the positive effects of bacteria on
environmental preservation. These bacteria can clean up oil slicks by
biodegrading some aromatic carbon compounds in oil spills. Others can digest
aromatic hydrocarbons, used in wood preservatives, which are harmful to the
soil. Another bacterium, which was discovered in 1997 in USA, named
Dehalococcoides Ethenogenes can remove chlorine from carcinogenic
chemicals that are used as ingredients in cleaning products and also digest DDT
(pesticide). These bacteria have the ability to convert toxic compounds that
contain chlorine to ethane which is harmless, in order to make water safer to
drink.
In conclusion, all these uses of bacteria and other microorganisms not
only as symbiotic microorganisms in our body but also as important factors in
industrial products and environmental preservation, depict clearly that
microorganisms are a lot more than just disease-causing agents, strongly able to
control life on earth.
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References
Books
1. Campbell and Reece, (2008). Biology: 27:571-572
2. Elliot R.P. et al, (1982).Microorganisms in foods 1:Their significance
and methods of enumeration: 5-6,11-13
3. El-Mansi E.M.T. et al, (2007).Fermentation Microbiology and
Biotechnology: 1-45,333-341
Articles
1. Advastar Communications, (2009). Microorganisms: friends or foes?
2. American Society for Microbiology, (2006). Probiotic Microbes: The
Scientific Basis
3. Halotec, (2008). Launch of new generation Alcohol Fermentation
Monitor (AFM)
4. Kiani L., (2006). Bugs in Our Guts—Not All Bacteria Are Bad
How Probiotics Keep Us Healthy. Proquest
5. Lodolo E. et al, (2008). The yeast Saccharomyces cerevisiae– the main
character in beer brewing. Federation of European Microbiological
Societies: 8:1018-1036
6. Osolin C. (2002). Researchers to toast 'good' bacteria Joint Genome
Institute 'jamboree' will examine the genetic properties of lactic-acidproducing microbes. Research news: 925: 296-5643
7. Science Daily, (2008). Bacteria in mouth help make certain foods tasty
8. Sigler K. et al, (2008). Net effect of wort osmotic pressure on
fermentation course, yeast vitality, beer flavor, and haze.
Biotechnological Products and process Engineering
Web pages
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http://www.typesofbacteria.co.uk/bacteria-deal-with-pollution.html
http://www.typesofbacteria.co.uk/bacteria-fix-nitrogen.html
http://www.typesofbacteria.co.uk/bacteria-recycle-nutrients.html
http://www.tempeh.info/fermentation/alcohol-fermentation.php
http://www.typesofbacteria.co.uk/friendly-bacteria-digestive-system.html
http://www.typesofbacteria.co.uk/friendly-bacteria-skin.html
http://www.typesofbacteria.co.uk/useful-bacteria-food.html
http://www.exploratorium.edu/cooking/pickles/fermentation.html
Picture taken from: http://www.vedicsciences.net/design/bacteria5.jpg
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