microbiology notes

the above

HideShow resource information
  • Created by: tania
  • Created on: 21-11-11 17:53
Preview of microbiology notes

First 398 words of the document:

B3-3 : Microbiology
Growing Microbes
The study of microorganisms is called microbiology. These include
bacteria, viruses and fungi, all too small to be seen by the naked eye. Many
microorganisms can be grown in a lab, where we can research them and
find out what they need to survive ­ and learn which are useful for us and
which want to kill us.
Learning more about microorganisms requires culturing them (i.e. growing
large numbers to see their behaviour as a colony). For this to happen, you
must provide them with everything they need: a culture medium with
carbohydrate(s) to act as an energy source, and necessary nutrients
(mineral ions, and sometimes proteins and vitamins ­ included). The
nutrients are usually contained in an agar medium ­ a substance which
dissolves in hot water and will set to form a jelly. Hot agar containing the
nutrients is poured into a Petri dish and left to cool before any
microorganisms are added. Warmth and oxygen is usually needed for
growth too.
Safety in the Lab
It is essential that all microbe culture is done carefully, even when growing
the safe microorganisms. This is because they can be pathogenic, and the
safe ones can mutate to become harmful pathogens. The other problem is
cross-contamination between microorganisms, which can upset
experiments ­ but more importantly is a health and safety issue when they
get onto human skin and you bring them everywhere with you.
Yeast is probably the most important
microorganisms for us. Yeasts are single-celled organisms with a nucleus,
cytoplasm and membrane surrounded by a cell wall. They reproduce by
asexual budding (splitting into two to form two new yeast cells).
Provided with a lot of oxygen, yeast cells will respire aerobically. They
break down sugar as an energy source, producing the waste products
carbon dioxide and water. However, sometimes there is a lack of oxygen, so
they respire anaerobically, which produces ethanol and carbon dioxide.
Ethanol is alcohol. And this process of anaerobic respiration in yeast cells
is called fermentation.
Like with humans, aerobic respiration is better for the cells because it
produces more energy. This energy allows them to grow and reproduce;

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Yeast is used to produce bread and alcoholic drinks. In bread production,
the yeast grows and respires ­ producing carbon dioxide which causes the
bread to rise. The gas bubbles expand when baked due to the high
temperatures, giving the bread its light, wafery texture. All yeast cells are
killed by the heat in the cooking process.
We can make beers and wines using yeast. Making beer relies on the
process of malting, where barley grains are soaked in water to keep them
warm.…read more

Page 3

Preview of page 3

Here's a taster:

Enzymes are also added to help separate
the milk ­ when it has completely curdled, you can see separate curds
from the liquid whey. The curds can then be used to make cheeses, whey
generally goes on to be animal feed.
Next, the curds are mixed with other bacteria and moulds and left to dry
out.…read more

Page 4

Preview of page 4

Here's a taster:

graph above shows bacterial growth for real-life conditions, not the
suitable, convenient conditions we give microbes in an industrial fermenter.
A new substance was discovered not long ago, a food based on fungi, and it
is called mycoprotein. It is produced using the fungus Fusarium, which
grows and reproduces very rapidly based on a cheap energy supply (an
inexpensive sugar syrup made from waste carbohydrates) in a large
fermenter. It does require areobic conditions to grow.…read more

Page 5

Preview of page 5

Here's a taster:

However, several months later they were
prepared and saved the life of a child. Unfortunately, Fleming's original
mould was hard to harvest on a mass scale, but a mould growing on a
melon was discovered which yielded more than 200 times the penicillin
from before. It was grown in deep tanks industrially, so that by 1945
enough was being produced to treat 7 million people a year.
Modern Penicillin Production
Nowadays we use modern strains of the Penicillium mould which give even
higher yields.…read more

Page 6

Preview of page 6

Here's a taster:

In China's biodigesters, they will put anything in there ­ vegetables, human
and animal faeces and urine, etc ­ which produces low quality gas but high
amounts of fertiliser.
On the other hand, in India (where there are social taboos against using
human waste), only animal waste is fed in ­ which produces high quality
gas, but very little amounts of fertiliser.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »