(2) The capsule is a gummy, jelly-like layer that surrounds most bacteria
and varies in thickness. This capsule offers the cell some protection against adverse
conditions, including drying. The capsule is the source of slime on beef carcasses.
(3) Cytoplasm is the internal environment of the cell, excluding the nucleus.
This is part of the actual living materials of the cell and the physical and chemical
changes that occur here produce life. A highly specialized structure in the cytoplasm is
the site of respiration of the cell. The cytoplasm is usually a clear, somewhat viscous
substance consisting of a complex mixture of proteins, fats, oils, carbohydrates,
minerals, and water.
(4) The nucleus or aggregates of nuclear material are in the central portion
of the cell. They transmit hereditary traits and contain the genetic controlling materials.
(5) Flagella are long, fine thread-like filaments attached to the cell in various
locations and they give movement or locomotion to the cell. Not all bacteria possess
(6) Endospores are produced by some bacilli (rod-shaped bacteria). The
endospore enables the bacterial cell to remain viable for long periods of time. It is much
more resistant to drying and other adverse conditions than the vegetative cells of the
species. Some bacterial spores are so resistant that they will live 20 years or more on
dry splinters of wood. They will grow after being subjected to strong disinfectant
solutions, and will survive for an hour in boiling water or a hot oven. The biologic
significance of endospores is not known, but because of their great resistance to heat,
drying, and chemicals, some bacteriologists argue that spores are produced to permit
survival under unfavorable conditions.
b. Shape and Size. Bacteria are spheroid, rod, or spiral in shape (figure 1-2).
Spheroid (or round-shaped) bacteria are called cocci (singular: coccus), rod-shaped
bacteria are called bacilli (singular: bacillus), and spiral-shaped bacteria are called
spirilla (singular: spirillum). See figure 1-2. The organisms causing food fermentation,
the soil bacteria, and most of the rot-producing bacteria are in the bacilli classification.
The extreme smallness of bacteria may be emphasized by the fact that 400 million
bacteria would occupy the volume of a grain of sugar. Bacteria are commonly
magnified about 1000 times for observation in the laboratory. A man magnified to the
same extent would be over a mile high and 500 yards wide.
c. Arrangement. Cells possessing a well-developed slime layer, or capsule,
tend to cling together, but cells without a capsule exist as single cells. Bacilli and spirilla
are arranged in chains, in irregular masses, or they may exist as single cells. Cocci
may exist as a diplococcus (paired), streptococcus (pairs or chains), staphylococcus
(clusters), tetracoccus (square clusters of four), or sarcina (cube clusters of eight with
formation of yellow or orange pigment). See figure 1-2. Bacteria often develop colonies
that are large enough to be seen without the aid of a microscope. These colonies are
simply masses of bacterial cells that may develop from a single vegetative cell, a single