2.1: Introduction

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In natural environments, microorganisms usually exist as mixed populations. However, if we are to study, characterize, and identify microorganisms, we must have the organisms in the form of a pure culture. A pure culture is one in which all organisms are descendants of the same organism. Techniques for obtaining pure cultures from a mixed population will be described in Lab 3. In working with microorganisms we must also have a sterile nutrient-containing-medium in which to grow the organisms. Anything in or on which we grow a microorganism is termed a medium. A sterile medium is one which is free of all life forms. It is usually sterilized by heating it to a temperature at which all contaminating microorganisms are destroyed. 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. This method of preventing unwanted microorganisms from gaining access is termed aseptic technique.

Caution

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!

Videos

Videos reviewing techniques used in this lab:

Contributors and Attributions

Dr. Gary Kaiser (COMMUNITY COLLEGE OF BALTIMORE COUNTY, CATONSVILLE CAMPUS)