Chapter 7 second week

Question 1

Microbial Measurement Methods: Direct

Answer 1

• Standard Plate Count
• Direct Observation (Petroff-Hausser)
• Most Probable Number
• Filtration
• Flow Cytometry

Question 2

Microbial Measurement Methods: Indirect

Answer 2

• Optical density
• Turbidity
• Amount of Metabolic Products
• Dry Weight

Question 3

Pour Plate Method

Answer 3

1. Inoculate empty plate
2. Add melted nutrient agar
3. Swirl to mix
4. Colonies grow in and on solidified medium

Question 4

Spread Plate Method

Answer 4

1. Inoculate plate containing solid medium
2. Spread Inoculum over surface evenly
3. Colonies grow only on surface of medium

Question 5

Standard Plate Count Using Serial Dilutions

Answer 5

Direct microbial measurement method
(start with something not dilute and make it dilute; ex of serial dilutions: milk)
-To obtain a countable plate
1. Flask inoculated
2. Samples taken at equally spaced intervals
3. Sample is diluted in liquid agar medium and poured or spread over surface of solidified medium
4. Plates are incubated, colonies are counted
5. Number of colonies (CFU) per 0.1 ml
-Tubes will be increasingly dilute–> less organisms will grow

Question 6

Serial Dilutions

Answer 6

• 1:10= most organisms
• 1:100= second most
• 1:1000= less organisms, probable count

Question 7

Direct Microscopic Count Of Bacteria with a Petroff-Hausser Cell Counter

Answer 7

Direct Microbial Measurement Method
-count bacteria individually
-count bacteria in squares when you look under microscope
(you multiply by volume then multiply by ml in test tube)
-every method has drawbacks

Question 8

Most Probable Number (MPN) Dilution Series

Answer 8

A direct microbial measurement method
A Statistical Estimate
a. MPN (1st set of tubes: 10ml = all 5 positive, 2nd: 1ml= 3 positive tubes, 3rd: 0.1 ml= 1 positive tube out of 5 tubes)
b. MPN Table- enables us to calculate for a sample the microbial numbers that are statistically likely to lead to such a result. ex: the # of positive tubes recorded for each set: 5,3,1; you would then look up that sequence in the table

Question 9

Filtration

Answer 9

A direct microbial measurement method
(another method for water testing)
a.) the bacteria in 100ml of water were sieved out onto surface of a membrane filter
b.) a filter, with the bacteria much more widely spaced, was placed on a pad saturated with liquid Endo medium, which is selective for gram-negative bacteria. The individual bacteria grew into visible colonies. One hundred twenty-four (124) bacteria per 100ml of water sample

Question 10

Flow Cytometry

Answer 10

A direct microbial measurement method

• helps come up with a # of bacteria
• requires a computer and a laser beam
• permits reliable detection of single or multiple microbes and can provide info about their distribution within cell population

Question 11

Spectrophotometer

Answer 11

A Indirect microbial measurement method

• Measures absorbance or optical density (OD) (Light)
• amount of light getting through; more bacteria less light, less bacteria more light

Question 12

Turbidity

Answer 12

A Indirect microbial measurement method

-cloudiness

Question 13

Metabolic Activity

Answer 13

(A Indirect microbial measurement method)
Assumes the amount of metabolic product such as CO2 or acid or alcohol is in direct proportion to the number of bacteria present
-Product amount= # of bacteria

Question 14

Dry Weight

Answer 14

(A Indirect microbial measurement method)
Best method for filamentous bacteria (e.g. Actinomyces) or molds
-The weight or mass of organic matter or soil after removal of water by heating to constant weight
-The dry weight of cells is the weight left when their water content has been removed by heating

Question 15

Microbial Associations

Answer 15

• Symbioti

- Nonsymbiotic

Question 16

Microbial Associations: Symbioti

Answer 16

Organisms live in close nutritional relationships; required by one or both members

Question 17

Microbial Associations: Nonsymbiotic

Answer 17

Organisms are free living; relationships not required for survival

Question 18

Examples of Microbial Associaitons Symbioti

Answer 18

1. Mutualism
2. Commensalism
3. Parasitism

Question 19

Examples of Microbial Associations Nonsymbiotic

Answer 19

1. Synergism (Syntrophy)

2. Antagonism

Question 20

Symbioti: Mutualism

Answer 20

Obligatory, dependent; (or non obligatory) both members benefit

Question 21

Symbioti: Commensalism

Answer 21

The commensal benefits; other member not harmed

-relationship where one organism benefits and the other does not but is not harmed

Question 22

Symbioti: Parasitism

Answer 22

Parasite is dependent and benefits; host harmed
-Parasite lives off another (host) and causes harm to the host
ex: Endoparasites: lives on inside of host (tapeworm)
Ectoparasites: Lives on outside of host (ticks, fleas, mosquito)
Facultative parasites: parasite that can use a host or not; can survive without host but if there is one it will use it

Question 23

Endoparasite

Answer 23

lives on inside of host (tapeworm)

Question 24

Ectoparasite

Answer 24

lives on outside of host (ticks, fleas, mosquito)

Question 25

Facultative Parasites

Answer 25

parasite that can use a host or not; can survive without host but if there is one it will use it

Question 26

Nonsymbiotic: Synergism (Syntrophy)

Answer 26

members cooperate and share nutrients

Question 27

Nonsymbiotic: Antagonism (Amensalism)

Answer 27

some members are inhibited or destroyed by others