question
Bacterial species that form a __________ zone of inhibition are more sensitive to the given compound.
answer
larger
question
Coliform bacteria characteristics
answer
1. Rod shaped
2. Gram (-)
3. Do not produce endospores
4. Ferment lactose in the presence of bile, producing acid and gas (35-37C)
5. Produce metallic green sheen on EMB plates
2. Gram (-)
3. Do not produce endospores
4. Ferment lactose in the presence of bile, producing acid and gas (35-37C)
5. Produce metallic green sheen on EMB plates
question
Fecal coliforms
answer
Coliforms that are commonly associated with the gastrointestinal tract of humans; thermotolerant (44.5C)
question
Coliforms and fecal coliforms do or do not always indicate human fecal contamination?
answer
Do not; considered imperfect indicator organisms
question
EMB plate: what is it & what does it do?
answer
Eosin methylene blue agar (EMB)
-->selective and differential -->isolates fecal coliforms
-->inhibits the growth of most Gram + .
-->selective and differential -->isolates fecal coliforms
-->inhibits the growth of most Gram + .
question
EMB Plate: (positive vs negative results)
answer
Positive: turns medium dark purple; if slow/weak = pink colonies
Negative: if colorless = no fermentation+not fecal coliform
Negative: if colorless = no fermentation+not fecal coliform
question
EMB Plate: Differential & Selective properties
answer
Differential: Sucrose/ Lactose fermentation If the organism
Selective: shows growth of fecal coliforms
Selective: shows growth of fecal coliforms
question
How would E. coli look on an EMB plate?
answer
Escherichia coli, a vigorous fermenter, often produces a green metallic sheen.
question
What are the important microbes for fermentation process?
answer
1. lactic acid bacteria
2. acetic acid bacteria
3. propionic bacteria
4. yeast (saccharomyces cerevisiae)
2. acetic acid bacteria
3. propionic bacteria
4. yeast (saccharomyces cerevisiae)
question
Lactic Acid bacteria: characteristics
answer
1. gram +
2. acid-tolerant
3. generally nonsporulating
4. non-respiring
5. either rod or coccus shaped
2. acid-tolerant
3. generally nonsporulating
4. non-respiring
5. either rod or coccus shaped
question
MacConkey plate: (positive vs. negative results)
answer
Positive: Pink/Red colonies = coliform bacteria so can ferment lactose (bubbling/foaming indicates capable of catalase activity (H2O2 -> O2 + H2O)
Negative: Cream colonies
Negative: Cream colonies
question
Do lactic acid bacteria have catalase?
answer
No
question
MacConkey plate: Differential & Selective properties
answer
Differential: Coliforms = can do Lactose fermentation (produces acid and drops pH of media which alters pH indicator in the media);
Selective: Gram - bacteria grow on it; bile salts and crystal violet inhibit growth of gram +
Selective: Gram - bacteria grow on it; bile salts and crystal violet inhibit growth of gram +
question
TSA plate
answer
Tryptone Soy Agar medium
question
TSA Plate: Differential and Selective properties
answer
Tryptic Soy Agar;
-Non-selective
-Non-differential
-Non-selective
-Non-differential
question
TSA plate: purpose
answer
Supportive medium that supports growth of all microorganisms that do not require special nutrients.
question
Microcentrifuge tube
answer
small, cylindrical, plastic container with conical bottom; used to store and centrifuge small amounts of liquid
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