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OBTAINING PURE CULTURES
Most samples from natural conditions contain many different species of bacteria, and often other
types of microbes as well. Each microbe placed on the surface of a solid medium grows and
forms a visible colony. Colonies formed by different microbes may have different appearances. In
obtaining, a pure culture, one that contains only one type of microbe, the goal is to thin out the
original microbes so that the resulting colonies are separate from each other. This can be done in
several ways:
1. Streak plate
2. Pour plate
3. Spread plate
4. Micromanipulator
METHODS OF PRESERVING BACTERIAL CULTURES
1. Refrigeration—short-term
2. Deep-freezing in liquid suspending medium-- temperature quickly lowered to -50
o
C to -95
o
C.
Years.
3. Lyophilization (freeze-drying)—microbes are quickly frozen while the water content is
removed at the same time (formation of ice crystals is damaging to cells). The result is a dry
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- Fall '09
- SMITH
- Bacteria, filamentous bacteria, bacterial cultures, Reproductive spores, Sporessome filamentous bacteria, visible colony. Colonies, liquid suspending medium
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