Lab 6: Environmental Factors that Effect Microbial Growth and Introduction to Special Media Flashcards
Three environmental factors that affect growth:
- Oxygen
- pH
- Temperature
Obligate Aerobes
Only grow aerobically
* In the presence of oxygen (aerobically)
Obligate Anaerobes
Only grow anaerobically
* Are unable to use oxygen and are harmed by it
Facultative Anaerobes
Grow aerobically or anaerobically
* Can grow with or without oxygen
Aerotolerant Anaerobes
Grow in the presence of oxygen because these microorganisms can tolerate it
* Cannot use oxygen for metabolic purposes
Microaerophiles
Grow only aerobically
* Differ from obligate aerobes because concentrations of oxygen lower than air are required for growth
Obligate Aerobes
Obligate Anaerobes
Facultative Anaerobes
Aerotolerant Anaerobes
Microaerophiles
Aerotolerate Anaerobe
Facultative Anaerobe
notice the pink media at the top of the test tube indicating the presence of O2
Obligate/Strict Anaerobe
Obligate/Strict Aerobe
notice the pink media at the top of the test tube indicating the presence of O2
Microaerophile
Resazurin
Turns media pink indicating presence of O2
O2 has been reduced
colorless
Presence of O2
media turns pink
Identify A:
Facultative Anaerobe
since it grew in both aerobic and anaerobic conditions
Identify B:
Obligate Anaerobe
because only grew in anaerobic jar
Identify C:
Obligate Aerobe
because only grew in aerobic conditions
Identify D:
Facultative Anaerobe
Psychrophile
below 20°C
Psychrotroph
0°C - 30°C
Mesophile
15°C - 45°C
(human pathogen)
Thermophile
above 45°C
Extreme Thermophile
above 65°C
Acidophile
Acidic environments below pH 5.5
Neutrophile
pH levels between 5.5 and 8.5
Alkaliphile
Alkaline/basic conditions above 8.5
Selective Media
Used to isolate microoorganisms by inhibiting the growth of some organisms while encouraging the growth of others
Differential Media
Media that contains indicators, which help differentiate microorganism based on a variety of factors
(ex. fermentation)
Mannitol Salt Agar (MSA)
Used for the isolation and differentiation of Staphylococcus
* Testing for the inhibition of growth by NaCl and Mannitol fermentation
Only Staphylococcus genus are able to grow on this media
Mannitol
Carbohydrate serves as the substrate for fermantation
* is what makes MSA differential
(only microorganism that are able to ferment mannitol will produce acid by products turning the media (MSA) acidic and triggering the indicator to turn yellow)
Sodium Chloride
7.5% Sodium Chloride (NaCl) concentration
* makes it selective
(only microorganisms that area able to grow in high concentration of salt will grow on MSA media)
Phenol Red
Indicator for fermentation of mannitol
Yellow = Acidic (+)
What is A dipicting?
Inhibition of growth
What is B dipicting?
(+) Growth
(-) Fermentation
What is C depicting?
(+) Growth
(+) Fermentation
MacConkey Agar (MCA)
Used for the isolation of Gram (-) microorganisms - coliforms
- Testing for the inhibition of Gram (+) growth by bile salts and crystal violet within the media and lactose fermentation
Only Gram (-) will grow on MCA
Lactose
MacConkey Agar (MCA)
Carbohydrate serves as the substrate for fermentation
* Makes MCA differential
**(only microorganism that are able to ferment Lactose will produce acid by products turning the media acidic and triggering the indicator to turn pink → colonies will appear pink)
Bile Salts and Crystal Violet
Are within the media and inhibit the growth of Gram (+) microorganisms
* Make MCA selective
(only microorganisms that area able to grow in or tolerate the presence of bile salt and crystal violet will grow on this media)
Neutral Red
Indicator for fermentation of lactose
- Red/pink colonies → decrease in pH → Acidic ( + for lactose fermentation)
- Colorless colonies → pH 6.8 or higher → ( - for lactose fermentation)
Neutral Red
Colorless Colonies
pH 6.8 or higher
* ( - for lactose fermentation)
Neutral Red
Red/Pink Colonies
Decrease in pH
* Acidic ( + for lactose fermentation)
Identify A
Lactose negative
Identify B
Lactose positive
Identify C
Lactose positive
Eosin Methylene Blue (EMB)
Used for the isolation of Gram (-) microorganisms - coliforms
* Testing for the inhibition of Gram (+) growth by eosin y and methylene blue dye within the media and lactose fermentation
Lactose
Eosin Methylene Blue (EMB)
Carbohydrate serves as the substrate for fermentation
* Makes EMB media differential
(only microorganisms that area able to grow in or tolerate the presence of Eosin y and Methylene Blue will grow on this media)
Dyes
Eosin Methylene Blue (EMB)
Indicator for fermentation of lactose / pH indicator → increases dye absorption by the colonies
Eosin Methylene Blue (EMB) Dyes:
Purple/pink colonies
decrease in pH → Acidic (+) for lactose fermentation and (-) for coliforms
medium lactose fermenters
Eosin Methylene Blue (EMB) Dyes:
Metallic green sheen
decrease in pH → Acidic (+) for lactose fermentation and (+) for coliforms
vigorous lactose fermenters
Dark Purple-Black
(+) for lactose fermentation
agressive lactose fermenter
Eosin Methylene Blue (EMB) Dyes:
Colorless colonies
pH 6.8 or higher → Neutral/ Basic (-) for lactose fermentation and (-) for coliforms
Identify A
Lactose negative
colorless colonies
Identify B
Lactose positive
medium lactose fermenter
purple/pink colonies
Identify C
Lactose positive
agressive lactose fermenter
metallic green sheen
Fastidious organisms
Require special growth factors such as blood, brain extracts, vitamins, etc.
Beta-hemolysis
Alpha hemolysis
Gamma hemolysis
