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Bacteria are the smallest living things with a cellular structure; each individual bacterium
consisting of one single colorless cell, which is usually either spherical or rod-shaped.
Individual bacteria measure from 0.0001 inches to 0.00001 inches in length, so they can be
seen only with the help of a high-power microscope. They are so small that they can float
in the atmosphere, usually as 'passengers' on dust particles, up to a height of several thousand
feet, except immediately after a heavy downpour, when the air is washed clean.
Bacteria are present in all natural as well as in drinking water that has not been purified
or bailed. A large number of bacteria live in the soil, down to a depth of several feet, and
they are particularly abundant in faeces and sewage. Thus, living bacteria are always present
on the surface of our bodies and on everything around us, but they are seldom found inside
the tissues of healthy plants and animals.
Since most kinds of bacteria contain no chlorophyll, they cannot use light energy and
Synthesize their food. They have to get their food in other ways, mostly ready-made by other
living things. Like plants, it can only take in dissolved food. A majority get their supply from
dead remains of other organisms.
Bacteria reproduce by dividing into two, and these new individuals grow so quickly that
they are ready to divide again in about half an hour. Hence, in ten hours, under the most favorable conditions, a single bacterium can produce over a million bacteria. That is one reason
for it being so difficult to ensure any object is completely free from any kind of living organisms.
In addition, some forms of bacteria have a waxy envelope outside their cell wall and are thus
more difficult to kill.
Few bacteria can long survive a temperature above 80°C in the presence of moisture. Hence,
when food items are boiled, nearly all the bacteria present is killed. Pasteurization is a milder
heat treatment that destroys the bacteria in milk.
The rate of multiplication of bacteria is greatly slowed down at temperatures below 10°C.
This means that food will remain unaffected by bacteria in a refrigerator.
Drying is also another method of preserving food and this dehydration of foodstuff prevents
bacteria from growing and multiplying as there is insufficient
moisture. |
