Microbiology - Steele




Growing Microbes. Microbes can be grown or cultured outside of a host or their environment using nutrients. This is called media. Some media are just broths, kind of like soup while others are solids. In order to make the media solid, agar is added to the media as shown on the left. Each one of those blobs is a colony of a microbe. They are growing separately on the surface and embedded in the agar.



Disease causing microbes. Microbes that cause disease are called pathogens. Handwashing is a good way to prevent transmission of pathogens. The Centers of Disease Control is an excellent source of information concerning pathogens (http://www.cdc.gov/). In addition, they post recommendations for ways to prevent transmission of specific pathogens (example H1N1) in addition to handwashing:




Microbes in the news. On September 12, 2009 a news story came out about MRSA on public beaches. What is MRSA and is it a problem? You will do a "Treasure Hunt" about this bacterium and learn about its characteristics. In addition to the questions asked, consider where MRSA usually thrives and contrast this to the beach. How could transmission occur?

Isolating microbes. In the picture above a microbiologist is holding a blood agar plate that is growing MRSA. As explained above, this is a type of media. Blood is commonly used as a medium since it is so rich in nutrients. You will also notice that there are clumps of the bacterium growing as isolated colony forming units or CFU's. In lab you are going to do a "four way streak for isolation" as shown in the plate above. The following video shows the basics. As you watch the video, please note the following:

  • the student is performing good aseptic technique by keeping the lid over the plate and working with it at an angle
  • the loop is flamed in between each streaking area or quadrant

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 Agar. (2009). In Wikipedia. Retrieved September 15, 2009 from http://en.wikipedia.org/wiki/Agar.


Aseptic technique. (2009). In Encyclopedia of Surgery. Retrieved September 15, 2009 from http://www.surgeryencyclopedia.com/A-Ce/Aseptic-Technique.html.


Colony forming units.(2008). In Biology Online. Retrieved September 15, 2009 from http://www.biology-online.org/dictionary/Colony-forming_unit.


Pathogens. (2009) Retrieved September 15, 2009 from http://www.medterms.com/script/main/art.asp?articlekey=6383.