Microbial Growth

Question 1

Slime

Answer 1

Biofilms have a matrix

of polysaccharides, DNA, and proteins

Question 2

Quorum sensing

Answer 2

Cell-to-cell chemical communication

Question 3

Microbes in biofilms

Answer 3

1000 times more resistant to microbicides.

Question 4

What percent of bacterial infections involve biofilms?

Answer 4

70%

Question 5

Culture Media

Answer 5

Any nutrient material prepared for the growth of microorganisms in the laboratory.

Question 6

Culture

Answer 6

The growth that results

Question 7

Should culture media be sterile?

Answer 7

YES!

Question 8

Problems with gelatin as a culture media

Answer 8

Melts at room temperature (23 C) and microbes use it for food.

Question 9

Agar

Answer 9

Derived from seaweed and is used as a solidifying agent as culture media.

Question 10

Benefits of Agar

Answer 10

Melts at/near boiling point (98-100 C) and resolidifies at (40 C)

Question 11

Chemically Defined Media

Answer 11

The exact chemical composition is known.

EXPENSIVE

Question 12

Complex Media

Answer 12

Most common media in which the chemical composition varies.

CHEAPEST

Question 13

Selective Media

Answer 13

Suppress the growth of unwanted bacteria and promote the growth of desired microbes.

Question 14

What can be used as a selective media?

Answer 14

Inhibitory chemicals (salt)
Antibiotics

Question 15

Differential Media

Answer 15

Makes it easier to distinguish colonies of desired colonies growing on the same plate.

Question 16

Alpha hemolysis

Answer 16

Causes green discoloration.

Question 17

Beta hemolysis

Answer 17

Completely destroys all the cells.

Question 18

Gamma hemolysis

Answer 18

Nothing happened.

Question 19

Streptococcus pyogenes

Answer 19

Only member of Group A streptococci, causes beta hemolysis and is the causative agent of strep-throat

Question 20

Pyrogenic

Answer 20

Creates pus

Question 21

Streptococcus agalactiae

Answer 21

Only member of Group B streptococci, causes beta hemolysis and is the causative agent of neonatal sepsis.

Question 22

Fermentation of lactose

Answer 22

Used to distinguish some

Intestinal pathogens from nonpathogens.

Question 23

Pathogenic, non-lactose fermenters

Answer 23

Salmonella and Shigella

Question 24

E.Coli

Answer 24

Ferments lactose to acid products.

Question 25

Some media are ____ selective and differential

Answer 25

Both

Question 26

How do we obtain a pure culture?

Answer 26

Streak Plate method is the most common.

Question 27

Streak Plate Method

Answer 27

(1) Inoculating material with mixed organisms onto quadrant #1. (2) Using sterile loop, streak some of the material into quadrant #2. (3) repeat using sterile lol each time tell you have 4 quadrants.

Question 28

Results of a Streak Plate

Answer 28

Isolated colonies from only one bacterium (genetically identical), can be transferred to new agar plate for a pure culture.

Question 29

Deep Freezing

Answer 29

Happens at (-50 C -95 C) Good for Years

Question 30

Freeze-drying (lyophilization)

Answer 30

Bacterial culture is frozen and the water is removed by a high vacuum. Good for years/decades

Question 31

``` Generation time (doubling time) ```

Answer 31

The time it takes the population of bacteria to double.

Question 32

Escherichia coli

Answer 32

20-30 minutes

Question 33

Mycobacterium Tuberculosis

Answer 33

1 day

Question 34

Mycobacterium Leprae

Answer 34

14 days

Question 35

Rapid doubling time causes symptoms ______.

Answer 35

Faster

Question 36

Lag Phase

Answer 36

A period of little or no cell growth but INTENSE METABOLISM while the cells adjust to a new environment.

Question 37

Log Phase | (exponential growth phase)

Answer 37

Period that the cells are reproducing most actively. | Cellular respiration is most active! Yeah

Question 38

Stationary Phase

Answer 38

Growth slows and deaths equal the number of births - less nutrients - toxic ware

Question 39

Death Phase

Answer 39

Number of deaths exceeds the number of births. | -can go to extinction

Question 40

Bacteria in stationary phase are ______ to respond to antibiotics, like penicillin

Answer 40

Unlikely, lancing reduces pressure, drains pus, restores blood flow, and returns the remaining bacteria to log phase to be treated with antibiotics.

Question 41

Standard Plate count

Answer 41

A way to the determine viable numbers of microbes that are present. COUNTS ONLY LIVING BACTERIA

Question 42

Filtration

Answer 42

Estimating bacterial populations when the quantity of bacteria in the sample is very low. ONLY COUNTS LIVING ORGANISMS

Question 43

Direct Microscopic count

Answer 43

Using a measured volume of bacteria suspension and a special counting chamber. COUNTS LIVING AND NON-LIVING

Question 44

Direct electronic counting

Answer 44

Special machines that count bacteria as they pass through a sensor. COUNTS LIVING AND NON-LIVING

Question 45

Turbidity (cloudiness)

Answer 45

The degree of turbidity indicated the population density. Can be measure with photodetector