How would you convince a friend that microorganisms

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20 Φεβ 2013 (πριν από 4 χρόνια και 8 μήνες)

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Student name: sa354

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Student name: sa354

Module: Microbiology

Lecturers
: Dr. Shaun Heaphy & Dr. Martha Clokie




Student name: sa354

1


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 pathoge
ns causing diseas
es 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 man
y

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 c
racks 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

produc
tion 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 bact
eria 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 bact
eria
never existed
in our intestine they would not produce their enzymes which are


Student name: sa354

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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
infectio
ns 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 cho
lesterol and can even prevent cancer
. Gene
rally
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 varie
ty

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 micro
organisms 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 spoilage
-
sensitive

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 u
sed is
Saccharomyces

cerevisiae

(yeast).

Most profitable temperature is 30˚C and the


Student name: sa354

3


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 fo
r 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 fu
nctions
, because c
arbon 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 ha
ppens 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 i
nvolved 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 i
n 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


Student name: sa354

4


can develop and survive.

These bacteria live in the roots of plants and produ
ce
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 canno
t 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 wh
ich 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 produc
e 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 conditi
ons.


More advantages are gained by the positive effects of bacteria on
environmental

pre
servation. These bacteria can clean up oil slicks by
biodegrading some aromatic carbon compounds in oil spills. Others can digest
aromatic hydrocarbons,

used in wood p
reservatives
,

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.








Student name: sa354

5


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).

L
aunch 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
-
acid
-
producing 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

1.

http://www.typesofbacteria.co.uk/bacteria
-
deal
-
with
-
pollution.html

2.

http://www.typesofbacteria.co.uk/bacteria
-
fix
-
nitrogen.html

3.

http://www.typesofbacteria.co.uk/bacteria
-
recycle
-
nutrients.html

4.

http://www.tempeh.info/fermentation/alcohol
-
fermentation.php

5.

http://www.typesofbacteria.co.uk/friendly
-
bacteria
-
digestive
-
system.html

6.

http://www.typesofbacteria.co.uk/friendly
-
bacteria
-
skin.html

7.

http://www.typesofbacteria.co.uk/useful
-
bacteria
-
food.html

8.

http://www.exploratorium.edu/cooking/pickles/fermentation.html

Picture taken from: http://www.vedicsciences.net/design/bacteria5.jpg



Student name: sa354

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