Microbial Growth

Question 1

Microbial growth -

1. when speaking of reproductive activities of microbes, use the term ___ to refer to an increase in the size of a population of microbes
2. Define colony
3. Define Biofilm

Answer 1

1. growth
2. aggregation of cells arising from a single parent cell (same type)
3. collection of microbes in a complex community (different types)

Question 2

What are they seven types of growth requirements?

Answer 2

1. oxygen
2. temperature
3. pH
4. moisture
5. osmotic pressure
6. light
7. food

Question 3

Oxygen -

1. how much oxygen do microorganisms need for growth?

Answer 3

1. microorganisms vary widely in their oxygen requirements for growth (aerobic and anaerobic)

Question 4

What is the most important factor affecting the growth of microorganisms?

Answer 4

temperature, bacteria can grow within a range of temps

Question 5

What are the three ways to classify organisms based on temperature?

Answer 5

1. Psychrophilic
2. mesophilic
3. hyperthermophilic

Question 6

Psychorphilic -

1. prefer ___ temps
2. these organisms take part in ___ of refrigerated foods

Answer 6

1. cold

2. spoilage

Question 7

Mesophilic -

1. prefer ___ temperatures
2. usually about ___ temperature
3. this is the ___

Answer 7

1. moderate
2. normal human body temp
3. MC

Question 8

Hyperthermophilic -

1. prefer ___ temps

Answer 8

1. high

Question 9

pH -

1. most microorganisms thrive in a pH range of ___
2. most animal pathogens work best near a pH of ___
3. “pickling” or preserving food may be accomplished in ___

Answer 9

1. 6-9
2. 7
3. acidic medium (vinegar)

Question 10

Moisture -

1. ___ and ___ requires water
2. __ and ___ are transported through the ___ in water solutions
3. water is a building material necessary in ___

Answer 10

1. vegetative cell maintenance and growth
2. food and waste, cell wall
3. cell synthesis

Question 11

Osmotic Pressure -

1. created by ___
2. ___= water drawn out of the cell, what happens (___)
3. ___= water is drawn into the cell, what happens

Answer 11

1. osmosis
2. hypertonic environment, cell may shrink and die (crenation(=)
3. hypotonic environment, cell may swell or burst

Question 12

Light -

1. __ and ___ pigmented bacteria use light as a source of part or all of their energy
2. in comparison ?
3. both (2) harm bacteria

Answer 12

1. green and purple
2. most pathogens are killed by direct sunlight
3. UV rays and warmth

Question 13

Food -

1. organisms require food for building (2) and for ___
2. microbial activity is ___ when food supplies become exhausted
3. the __ and ___ of food available will have an impact on the organism’s survival and growth

Answer 13

1. cell components and proteins, energy necessary for cell survival
2. limited
3. amount and type

Question 14

Culture Media -

1. some microbes are not particular and can be grown in a variety of media, others require ___
2. List two types of media

Answer 14

1. specific nutrients

2. selective and differential

Question 15

Defined Media -

1. exact chemical composition is ___
2. usually composed of ___

Answer 15

1. known

2 pure biochemical off the shelf

Question 16

Complex Media -

1. exact chemical composition is ___
2. usually contain complex materials of biological origin such as (4)
3. can support ___

Answer 16

1. unknown
2. blood, milk, yeast extract, or beef extract
3. a wider variety of microorganisms

Question 17

Selective Media -

1. contain substances that ____ the growth of particular organisms
2. ___ or ___ are added; ___ left out
3. example
4. explain

Answer 17

1. favor or inhibit
2. dyes or salts, specific nutrients
3. Sabouraud dextrose agar
4. inhibit growth of all bacteria, is selective of fungus

Question 18

Differential Media -

1. presence of ___ changes in medium or differences in the ___ of colonies help differentiate organisms
2. example
3. explain

Answer 18

1. visible, appearance
2. blood agar
3. different streptococcus organisms react differently, change appearance of blood sugar

Question 19

List and example of both selective and differential media and explain

Answer 19

MacConkey agar - selective for Gram (-) bacteria, also differentiates b/w types of gram (-) organisms