Bacteriology 102:
A "General Review" of the
Enrichment and Isolation
Experiments

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Enrichment & Isolation Review
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Modified:
5/17/06

This page covers Experiments 10.2, 11.1, 11.2 and 11.3. (We no longer do Exp. 9.3.)
The lab manual referred to herein is referenced here.


I.  REVIEW OF THE GENERAL PROCEDURE FOR THE ENRICHMENT, ISOLATION AND IDENTIFICATION OF BACTERIA as shown on the main enrichment/isolation page:

ENRICHMENT AND ISOLATION PURE CULTURE WORK
SOURCE
MATERIAL
BROTH
ENRICHMENT
PLATING FOR
ISOLATION
STOCK
CULTURES
CHARACTERIZATION & IDENTIFICATION
•Consider inoculum: what organisms may or may not be present.
•May pre-treat inoculum, e.g., by heat-shocking.
•Usually is selective.
•May be skipped altogether.
•Usually selective or selective-differential – but not always!!  
Throughout procedure, appropriate media and incubation conditions must be considered.

II.  A "WORKSHEET" TO HELP US ORGANIZE AND SUMMARIZE THE SPECIFIC FACTORS that allow isolation of the various types of microorganisms in these experiments:

  10.2
Streptomyces
11.1
Purple "non-sulfur" photosynthetic bacteria
11.2
Bacillus
11.3
Free-living N2-fixing bacteria
Special properties of desired organism that can be exploited to help us "sort it out" from others.
Likely source material (habitat of organism or where the organism is a significant contaminant).  
 
     
Treat sample to enhance isolation?        
Need to use enrichment?        
Factors to consider for the enrichment & plating media:*
•Selective by restriction of nutrients or addition of selective agents?
•Special sources of C, N, energy?
 
 
 
 
(Why is 2nd plating medium an all-purpose medium?)
**    
Special incubation conditions?   **  
 
 
 
Detectable features of the desired organism that help us in picking and identifying it.   **    
Any special, additional tests on the isolates? (That is, tests not essential to identification to the genus level.)  
 
 
     

  *  For the desired type of organism, the medium/media must include the required elements (including trace elements) and whatever growth factors are needed. Note that these organisms are all heterotrophs and organotrophs. (A review of Appendix D in the manual is useful; it is also reproduced here.)

**  See question 11B on page 162 in the manual. How would we want to grow the purple non-sulfur photosynthetic bacteria to maximize their detection and minimize growth of other organisms – as phototrophs or as chemotrophs?


Return to the
Main Enrichment and
Isolation Page
.
Page last modified on 5/17/06 at 5:00 PM, CDT.
John Lindquist, Department of Bacteriology,
University of Wisconsin – Madison