3D).Ī colony is a visible mass of microorganisms growing on an agar surface and usually originating from a single organism or arrangement of organisms. Resterilize the inoculating loop by placing it in the microincinerator for 10 seconds (see Fig. Remove the loop and immediately close the lid.Ħ. This keeps the inoculating loop parallel with the agar surface and helps prevent the loop from digging into the agar.ĥ. 5, each time you flame and cool the loop between sectors, rotate the plate counterclockwise so you are always working in the "12:00 position" of the plate. 3C) of the plate and streak side-to-side as you pull the loop toward you. Always start streaking at the "12:00 position" (see Fig. In order to avoid digging into the agar as you streak the loop over the top of the agar you must keep the loop parallel to the the agar surface. These streaking patterns allow you to obtain single isolated bacterial colonies originating from a single bacterium or arrangement of bacteria (see Fig. Streak the loop across the surface of the agar medium using the either the pattern shown in Fig. Lift the edge of the lid just enough to insert the loop.Ĥ. Keep in mind that you must wear the correct Personal Protection Equipment (PPE) in all labs where you are using microbial cultures, stains, chemicals, and glassware or microscope slides!ģ. This method of preventing unwanted microorganisms from gaining access is termed aseptic technique. Finally, in working with microorganisms, we must have a method of transferring growing organisms (called the inoculum) from a pure culture to a sterile medium without introducing any unwanted outside contaminants. It is usually sterilized by heating it to a temperature at which all contaminating microorganisms are destroyed.
VISUAL MICRO LAB FREE
A sterile medium is one which is free of all life forms. Anything in or on which we grow a microorganism is termed a medium. In working with microorganisms we must also have a sterile nutrient-containing-medium in which to grow the organisms. Techniques for obtaining pure cultures from a mixed population will be described in Lab 3. A pure culture is one in which all organisms are descendants of the same organism.
However, if we are to study, characterize, and identify microorganisms, we must have the organisms in the form of a pure culture. In natural environments, microorganisms usually exist as mixed populations.
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