MICROBIOLOGY PRE LAB QUIZ 3

When is an agent called a selective agent and medium called selective medium.

when an agent is incorporated into a medium that permits the growth of certain organisms while inhibiting or eliminating the growth of others.

There are many types of selective media which can be used in the _________________________.

recovery of an organism from a mixed culture

Many selective media are also ____________

differential

Differential media is designed to make distinctions ___________________ between different organisms growing on the ______________.

visibly possible, same medium

What are the functions of differential media?

enables one to make distinctions, to differentiate, between similar organisms on the basis of a biochemical or physiological property

In many cases microbiological media is both _________________

selective and differential

Why do we use Eosin Methylene Blue

gram-negative because of high dye content

Why is Eosin Methylene Blue differential for enteric organisms.

the medium contains the sugar lactose and organisms able to ferment this sugar are visibly differentiated from those that cannot

EMB

gram -, differentiates lactose fermenters from non fermenters, selective agent is eosin methylene blue (also differential agent), color e coli green lactose + pink lactose - colorless

PEA

selects gram + cocci, phenyl ethyl alcohol, none differential agent, colorless

MAC

selets gram - differentiates lactose fermenters from non fermenters, bile salts and crystal violetm differentiates neutral red lactose, lactose + pink red lactose - cream to colorless

MSA

selects staph differentiates manitol fermenters from non fermenters, NaCl salt, differentiates phenol red mannitol, mannitol + yellow zones, mannitol - no change in medium

Exercise 5 day one procedures

1. one plate of EMB, PEA, MAC, and MSA. mark divide plates in 4-6 equidistant sectors (according to # of microbes)

2. label for organisms and unkown

3. aseptic technique with loops and transfer to each plate flame between

4. incubate

Exercise 5 day two procedures

1. record growth and color

2A. yes, tolerates selective agent, go to B. no does not go to c

B. yes, ferments the sugar or has enzyme (c)]

no, does not (c)

C. the organism is most likely

3. Identify most like us limited to scope of media, may only determine likely gram reaction or differentiate in species

What element is important for microbial growth.

oxygen

What is it called when microbes cannot live in absence of oxyfen

strict aerobes

What are facultative aerobes

which can grow in either absence or presence of oxygen

What is microaerophillic

floursih in conditions where oxygen tension is reduced but not eliminated

What will you do in exercise 6

observe ways anaerobic conditions are achieved and lhow oxygen effects growth, examine sone of cultural, morphological and biochemical characteristics of some aerobic organisms

Exercise 6 procedure A

1. get 4 sterile tubes of thioglycollate broth and 2 plates of nutrient agar

2. label inoculate and incubate

3. put in quadrants label and inoculate

4. place one upside-down exposed to air and other in anaerobic jar

5. remove corner of hydrogen generator packet and place the packet and opened indicated strip against side of jar, add 10 mL of water and place lid, incubate

6. examone for growth, note relation to oxygen tension, record growth