iron, chlorine, sulphur, and phosphorus. More or less complex sources of carbon,
compounds, or from the elemental forms of these substances.
c. Deficiencies. Many bacteria have deficiencies in their synthetic abilities that
must be overcome before growth can follow. The vitamin B complex is the most
common source for this compound requirement. Other compounds often found
necessary for maximum growth are the amino acids, which are the building blocks of
d. Methods. There are two primary methods by which bacterial species secure
their food material. On this basis, bacteria are classified as follows:
(1) Saprophytes. These bacterial species get their food materials from the
dead bodies and waste materials of plants and animals. They also make some use of
inorganic compounds such as ammonia, nitrates, chlorides, phosphates, and sulfates.
Most of the saprophytes are harmless to man. Two exceptions are Clostridium
botulinum and Clostridium tetani.
(2) Parasites. These bacterial species secure their nourishment from the
cells of plants or animals with which they intimately live. The parasitic bacteria are
mostly harmful to man.
1-19. OXYGEN REQUIREMENTS
Few processes have had such a wide variety of definitions as respiration. We
normally think of respiration as being synonymous with breathing, but a broader
meaning is necessary to identify bacterial respiration, which is accomplished without a
breathing apparatus. Bacterial respiration is any chemical reaction whereby energy is
released for life processes. The reactions are those that transform energy for the cell.
Energy transformations can take place under aerobic or anaerobic conditions or
combinations of these conditions. On the basis of their processes of respiration,
bacteria are classified as follows:
a. Aerobic bacteria require the presence of free or atmospheric oxygen for
b. Anaerobic bacteria do not require the presence of oxygen for growth and will
grow better in its absence.
c. Facultative bacteria will grow either with or without the presence of oxygen.
d. Microaerophilic bacteria require a definite but reduced amount of free oxygen