| Bacteria are
one-celled microorganisms. They have a cell wall
which gives it shape (some are also enclosed by a
capsule), a cell membrane just inside the cell
wall which encloses the [cytoplasm] and DNA which forms the
area of the cytoplasm called the nucleoid.
Bacteria are divided into groups according to
their shape: round bacteria are cocci, rod-shaped
are bacilli, (bent rods are vibrios) and
spiral-shaped bacteria are spirilla or
spirochetes. Two or more bacteria linked together
are described by prefixes diplo-(pair),
staphylo-(cluster), or strepto-(chain).
Most bacteria are parasites,
although a few manufacture their own food. Some
of these parasites are very helpful--they aid in
many bodily functions including digestion, and
help with other processes, such as decomposition
of soil and changing of milk into cheese. Disease
results, however, when bacteria multiply rapidly
(each cell simply divides into two identical
cells) and damage or kill the human tissue, as in
pneumonia and tuberculosis.
Diseases can also produce toxins that damage or
kill human tissue as in food poisoning or cholera. Sometimes
bacteria in the body are helpful for awhile, and
then something in the body or the bacteria
changes, casing destruction in the host. Segments
of DNA in the bacteria can be exchanged with
other bacteria when a cell divides in a process
called conjugation. This interchange of DNA
segments often results in disease. This makes
tracking and identification of a disease more
difficult.
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