Laboratory Cultivation of Microorganisms
Culturing an organism in the laboratory needs adequate supply of the nutrients the organisms
require and optimum conditions. The conditions and nutrients to be provided in the laboratory
must reflect those in the natural habitat of the organism
Obtaining Pure Cultures
Creating a pure culture is the initial step towards laboratory cultivation of microorganisms. This is
done by creating a streakplate. Bacterial suspension is spread on an agar plate using a wire
inoculating loop such that it progressively becomes more dilute. Individual cells are deposited on
the surface of the agar. After incubation at a suitable temperature, cell division occurs and a
bacterial colony develops because the solid surface does not allow for any movement and so all
the offspring remain in one place.
Growth Media
The growth medium may be defined or undefined. A defined medium may have some constituents,
depending on the organism’s nutritional requirements. An undefined medium may have a variable
composition. The composition of an undefined medium is not known and is not important. An
undefined medium is used to cultivate fastidious bacteria. It is less expensive and easier to supply
the nutrients needed by these organisms. Bacteria with unknown nutritional requirements are
cultured on this type of media.
Successful culturing of microorganisms requires provision of the appropriate physical and
nutritional requirements. The cultures are stored at low temperatures to suspend growth. Deep
freezing is used to preserve cultures for many years as it prevents the cells mutation or loss of
viability.
