To preserve microbial cultures

To preserve microbial cultures - bacteria is streaked...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
To preserve microbial cultures, they may be placed in the refrigerator to slow down the  metabolism taking place. Two other methods are deep-freezing and freeze-drying. For  deep-freezing, the microorganisms are placed in a liquid and frozen quickly at  temperatures below –50°C. Freeze-drying (lyophilization) is performed in an apparatus  that uses a vacuum to draw water off after the microbial suspension has been frozen.  The culture resembles a powder, and the microorganisms can be preserved for long  periods in this condition. Isolation methods. To obtain separated colonies from a mixed culture, various isolation  methods can be used. One is the streak plate method, in which a sample of mixed 
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: bacteria is streaked several times along one edge of a Petri dish containing a medium such as nutrient agar. A loop is flamed and then touched to the first area to retrieve a sample of bacteria. This sample is then streaked several times in the second area of the medium. The loop is then reflamed, touched to the second area, and streaked once again in the third area. The process can be repeated in a fourth and fifth area if desired. During incubation, the bacteria will multiply rapidly and form colonies (Figure 1 )....
View Full Document

This note was uploaded on 11/11/2011 for the course BIO 101 taught by Professor Pesthy during the Fall '07 term at Texas State.

Ask a homework question - tutors are online