BIO 304                            Lab Worksheet 3                          Spring 2006

 

NAME______________________________________________

 

Directions:  To complete this worksheet, answer the questions and fill in the definitions, then attach the indicated pages from the lab manual to the back of the sheet.

 

Coverage:

          Ex. 12 Special Media

          Introduction to Microbial Metabolism: read pages 95, 96.

          Ex. 13 Carbohydrate Catabolism

          Ex. 14 Carbohydrate Fermentation

 

Exercise 12 Objectives:

1.      understand the difference between complex (general purpose) media, selective, and differential and enriched media.

2.      Understand what the selective or differential or enriching chemicals/additives are in each of the media used in lab and why.

3.      Discover which Gram reaction correlates with growth on EMB or MSA.

4.      Recognize and use a dichotomous or identification key.

 

Exercise 12 Questions:

            Complete pages 93, 94 (Omit Critical Thinking Q#3) and attach to this sheet.

 

Exercise 13: Objectives:

1.      Understand the difference between oxidative and fermentative glucose utilization

2.      Understand the difference between an endoenzyme and an exoenzymes

3.      Be able to interpret O/F Glucose tubes and starch hydrolysis plates

 

Ex: 13 Questions:  Fill out the data side of pg. 99, then answer the questions 1-6 on page 100.  Omit all Critical Thinking questions.  Attach the sheet to this worksheet.

 

Exercise 14 Objectives:

1.      Define fermentation

2.      Describe how the fermentation tube is interpreted

3.      Understand and interpret the MR-VP test.

 

Exercise 14 Questions:

 

The key ingredients in the Fermentation broths are:

          carbohydrate

          peptone

          pH indicator

          inverted tube

 

1.      In a lactose fermentation broth, what is the carbohydrate?

     lactose

 

 

2.      What biomolecule does the peptone provide?

     Peptone is a rich source of protein, which can be used as both a carbon and nitrogen source

 

3.      Why is the pH indicator needed?

     To be able to observe if there has been fermentation to acid products

4.      What is the function of the inverted (Durham) tube?

 

          To trap any gas formed during fermentation

 

 

5.      Can you tell the precisce composition of the trapped gas is in these fermentation broths?

 

          No, you can not tell the composition of the gas.  The gasses formed during fermentation are usually carbon dioxide or hydrogen, but without different testing, you can’t tell which.

 

 

6.      What happens if the carbohydrate is used up during the growth of the bacterium?

 

          The organism will start using the peptone as a carbon source oxidatively.  As a result, the pH will rise due to protein breakdown, and the pH indicator will go from yellow to red or pink.

 

 

7.      The MR-VP broth is a GENERAL PURPOSE broth.  So, every organism should grow.  What then is the purpose of this test?

     To differentiate between organisms that use the mixed acid pathway of fermentation, or make the neutral product, acetoin with the butylene glycol pathway.

 

 

 

Definitions:

Selective media: Define, then give an example of a type of media used in lab that fits the definition.

          media with ingredients that inhibit the growth of unwanted organisms while encouraging the growth of the desired organism.  Example:  MSA or EMB

 

 

Differential media: Define, then give an example of a type of media used in lab that fits the definition.

          media that contains ingredients that allow the differentiation between organisms growing on the plate based on differences in metabolism.  Example:  MSA or EMB or blood agar

 

 

General Purpose media: Define, then give an example of a type of media used in lab that fits the definition.

          Non-synthetic media which encourages the growth of a wide range of organisms.

 

 

Enriched media: Define, then give an example of a type of media used in lab that fits the definition.

          Media that contains ‘more goodies’, to encourage the growth of fastidious organisms

          Example:  blood agar

 

Dichotomous (Identification) Key:   a binary decision tree that aids in the identification of the genus and species of an unknown culture

 

 

metabolism     the totality of biochemical reactions that occur in the cell

enzyme         a specialized biomolecule (usually protein), that catalyzed a specific reaction in the cell.

 

endoenzyme (give a specific example along with the definition)

          an enzyme that remains inside the cell: example; an enzyme of glycolysis

 

exoenzymes (give a specific example along with the definition)

          enzymes released or secreted: amylase, penicillinase

 

hydrolytic enzyme:    an enzyme that breaks down larger molecules into subunits by addition of water

 

carbohydrate: an organic molecule with carbon, hydrogen, and oxygen C(H2O)n

 

 

 

polysaccharide (give a specific example along with the definition)

          a carbohydrate made up of 3 or more sugars

ex: starch, cellulose, glycogen

 

monosaccharide (give a specific example along with the definition)

          a simple sugar: glucose

 

disaccharide (give a specific example along with the definition)

          two sugars: (glucose + galactose = lactose)

 

 

catabolism:  breaking down molecules with the release of energy ultimately stored in the form of ATP

 

 

anabolism: building up cellular components with the consumption of energy