Micro1009- Chapter 6 Microbial Growth

Front 1

Microbial Growth

Back 1

Refers to the number of cells, not the size of the cells

Front 2

Requirements for growth

Back 2

1. Physical

2. Chemical

Hint 2

2

Front 3

Physical requirements for growth

Back 3

1. Temperature

2. pH

3. Osmotic pressure

4. Oxygen

Front 4

Minimum growth temperature

Back 4

The lowest temperature at which a species will grow

Front 5

Maximum growth temperature

Back 5

The highest temperature at which a species will grow

Front 6

Optimum growth temperature

Back 6

The temperature at which a species grows best

Front 7

What is the most common method of preserving household food items?

Back 7

Refrigeration

Front 8

The more time it takes for food to cool, the more ____

Back 8

time it spends in the danger zone

Front 9

Danger zone

Back 9

60-120F

Front 10

Classifications of bacteria based on temperature requirements

Back 10

1. Psychrophiles

2. Psychtrophes

3. Mesophiles

4. Thermophiles

Front 11

Psychrophiles

Back 11

Cold loving microbes

Optimal range 0-20°C

Found in glaciers and the depths of the ocean

Front 12

Psychrotrophs

Back 12

Have a higher optimum temperature but will grow slowly at 0°C

Involved on food spoilage in your fridge

Front 13

Mesophiles

Back 13

Room to body temp

Optimal temperature range 20-40°C

All human pathogens!

Front 14

Thermophiles and Hyperthermophiles

Back 14

Optimal temperature range 40-100+°C

Found in hot tubs, bottoms of compost piles, saunas, and hot springs

Front 15

Most bacteria grow between __ - __ pH

Back 15

6.5-7.5

Front 16

Classifications of microbes based on pH requirements

Back 16

1. Acidophiles

2. Alkalophiles

Hint 16

2

Front 17

Acidophiles

Back 17

- a few bacteria can grow at pH below 4

- some can grow at pH 0-1

Front 18

What foods benefit from the common pH range of bacteria and how?

Back 18

Pickles, cheese, and sauerkraut are preserved from spoilage by acids produced during fermentation

Front 19

Alkaliphiles

Back 19

A few bacteria can grow at pH 9 and above

Front 20

Helicobacter pylori

Back 20

Rod shaped bacteria that lives around the pyloric sphincter in the stomach

Causes ulcers

Secretes urease

Front 21

Urease

Back 21

An enzyme that converts urea and water into ammonia and CO2

Front 22

How does ammonia affect Helicobacter pylori

Back 22

It raises the pH, allowing the bacteria to survive the acidity while it breaks down the mucous layer that protects the stomach from itself

Front 23

Hypertonic environments can cause ____ in bacteria, which ____.

Back 23

Plasmolysis

Inhibits growth

Front 24

Plasmolysis

Back 24

The process in which cells lose water due to the osmotic pressure that occurs in a hypertonic solution

The opposite of cytolysis

Front 25

What bacteria have adapted to living in hypertonic environments?

Back 25

Halophiles

Front 26

Extreme halophiles

Back 26

Can grow in the dead sea (30% salt)

Front 27

Classifications of bacteria based on oxygen requirements

Back 27

1. Obligate aerobes

2. Obligate anaerobes

3. Facultative anaerobes

4. Aerotolerant anaerobes

5. Microaerophiles

Front 28

Obligate aerobes

Back 28

Require O2 for survival

O2 is the final electron acceptor

Front 29

Obligate anaerobes

Back 29

Grow in the absence of O2

O2 is lethal to them

Front 30

Facultative anaerobes

Back 30

Can grow under both aerobic and anaerobic conditions

Growth is greater where oxygen is present

Front 31

Aerorolerant anaerobes

Back 31

Only anaerobic growth but continues in the presence of oxygen

Front 32

Microaerophiles

Back 32

Need only small amount of O2 to grow

Normal atmospheric conditions kill them

Front 33

Microaerophilic conditions

Back 33

O2: <16%

CO2: >4%

Use candle jar methodto create these conditions

Front 34

Normal atmospheric conditions

Back 34

O2: 21%

CO2: 0.3-0.03%

Front 35

Superoxide

Back 35

O2-

A free radical that is produced by all organisms

Highly toxic to cells

Must be neutralized

Front 36

How is superoxide toxic?

Back 36

It steals elections

Front 37

Superoxide dismutase

Back 37

An enzyme that neutralizes the superoxide molecule

Front 38

Equation showing superoxide dismutase neutralizing superoxide

Back 38

Front 39

Hydrogen peroxide

Back 39

H2O2

Highly toxic for cells and must be neutralized

Front 40

Catalase

Back 40

Enzyme that neutralizes hydrogen peroxide

Front 41

Equation showing catalase neutralizing hydrogen peroxide

Back 41

Front 42

What is another enzyme that can break down hydrogen peroxide?

Back 42

Peroxidase

Front 43

Why is O2 lethal to obligate anaerobes?

Back 43

They lack superoxide dismutase (to neutralize O2-)

and catalase (to neutralize H2O2)

Front 44

Special culture techniques for anaerobic bacteria

Back 44

1. Reducing media (fluid thioglycolate)

2. Gas pack anaerobic system

Front 45

Reducing media

Back 45

Fluid thioglycolate broth

- Contains sodium thioglycolate that binds to free O2

- contains resazurin

Front 46

Resazurin

Back 46

Anaerobic indicator that turns pink in presence of oxygen

Front 47

Gas pack anaerobic system

Back 47

Contains palladium catalyst

Front 48

Palladium catalyst

Back 48

Causes H+ to bind with O2 in the air

Front 49

Special culture technique for microaerophiles

Back 49

Candle jar:

Candle burns off some of the oxygen, but leaves enough for microaerophiles

Front 50

Pneumonic for the most important chemicals required for bacterial life

Back 50

CHONPS

carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur

Front 51

Other ions important for life

Back 51

Potassium

Magnesium

Calcium

Sodium

Chloride

Trace elements

Hint 51

6

Front 52

What is the most important requirement for life?

Back 52

Water (hydrogen and oxygen)

Front 53

Other than water, what is the most important requirements of life?

Back 53

Carbon

Front 54

What makes up half of the dry weight of bacteria?

Back 54

Carbon

Front 55

What contains carbon?

Back 55

Lipids

Carbohydrates

Protein

Nucleic acid

Front 56

What uses photosynthesis to fix carbon from carbon dioxide in the air?

Back 56

Autotrophs

Front 57

For what purpose is nitrogen required?

Back 57

The production of amino acids and nucleotides

Front 58

What can fix nitrogen from the air into usable forms?

Back 58

Cynobacteria and other bacteria

Front 59

_____ are critical in recycling nitrogen in the soil

Back 59

Bacteria

Front 60

For what is sulfur required?

Back 60

It is required to produce sulfur containing amino acids and certain vitamins

Front 61

What are some important sources of sulfur?

Back 61

Sulfate ion

Hydrogen ion

Hint 61

2

Front 62

Why is phosphorus necessary?

Back 62

It is used to produce nucleic acids, including ATP

Front 63

Trace elements

Back 63

Things like iron, copper, molybdenum, and zinc, which are required in very small amounts

Front 64

Growth medium is usually in what forms?

Back 64

A liquid, solid, or semisolid

Front 65

General ingredients of growth media

Back 65

Water

Carbon and energy source

Nitrogen source

Trace elements

Front 66

What could be used as a nitrogen source in growth media?

Back 66

Proteins or specific amino acids

Front 67

Optional ingredients in culture media

Back 67

- solidifying agent

- peptones

- body fluid

- pH buffer

- reducing agents

- selective agents that inhibit the growth of unwanted microbes

Front 68

Peptones

Back 68

Tissue extracts

Front 69

What is a common solidifying agent and why is it commonly used?

Back 69

Agar

It cannot be broken down by bacteria

Front 70

What is the purpose of reducing agents in culture media?

Back 70

They remove O2

Front 71

Classifications of chemical ingredients

Back 71

1. Chemically defined

2. Complex ingredients

Front 72

Chemically defined

Back 72

Pure chemical ingredients

Front 73

Complex ingredients

Back 73

Derived straight from plants, animals, and fungus

Front 74

70% of healthcare associated infections involve _____

Back 74

Biofilms

Front 75

Biofilms

Back 75

Microbial communities that form a slime or hydrogel that adhere to surfaces

Front 76

What is the function of biofilm?

Back 76

It allows bacteria to share nutrients and get rid of harmful waste

It shelters the bacteria from harmful environmental factors

Front 77

Within a biofilm, bacteria communicate cell-to-cell via ____

Back 77

Quorum sensing

Front 78

How do bacteria grow?

Back 78

They divide by binary fission

Front 79

Generation time

Back 79

Doubling time

The time required for a cell to divide into 2 cells

Front 80

What is the generation time of most bacteria?

Back 80

1-3 hours

Front 81

Generation time of E. coli?

Back 81

20 minutes

Front 82

Generation time of Mycobacterium tuberculosis

Back 82

24 hours

Front 83

Limiting factors to bacterial growth in the environment

Back 83

1. Lack of food, h2o, nutrients

2. Lack of space

3. Accumulation of metabolic wastes

4. Not ideal o2 levels

5. Changes in pH

6. Temperature

Hint 83

6

Front 84

Optimal pH for most bacteria

Back 84

6.5 - 7.5

Front 85

Phases of growth

Back 85

1. Lag

2. Log

3. Stationary

4. Death

Front 86

Lag phase

Back 86

- bacteria are first introduced to the environment media

- cells are active metabolically

- very little growth

- lasts 1hr to several days

Front 87

Log phase

Back 87

- Begins when bacteria start actively reproducing

- Exponential growth

- Population doubles every generation

- microbes are sensitive to adverse conditions

Front 88

Stationary phase

Back 88

- death rate = rate of reproduction

- cells begin to encounter environmental stress

- endospores would form here

Front 89

Death phase

Back 89

- death rate > rate of reproduction

- population is reduced to a small number of the most resistant bacterial cells, which will start the cycle over when conditions are favorable

Front 90

Direct measurement of microbial growth

Back 90

1. Plate count

2. Filtration

3. Direct microscopic count

Front 91

Plate count

Back 91

- most used method

- requires serial dilutions

Ex. Pour plate

Front 92

Pour plate

Back 92

- used to see anaerobic growth

- involves inoculating an empty plate and swirling the bacteria with melted agar

- results in bacterial growth on and in solidified media

Front 93

Spread plate

Back 93

- involves inoculating a plate that contains a solid medium and spreading the inoculum over the surface evenly

- results in bacterial growth on the surface of the solid medium

Front 94

Filtration

Back 94

Passage of liquid through a grid containing small pores (<.45 um)

Great for catching bacteria in water samples

Front 95

Direct microscopic count

Back 95

Known volume of bacterial suspension placed on special cell counting slide

Front 96

Indirect methods of estimating bacterial numbers

Back 96

1. Turbidity

2. Metabolic activity

3. Dry weight

Front 97

Turbidity

Back 97

Cloudiness produced as media becomes filled with bacteria

Gives immediate feedback

Front 98

Spectrophotometer

Back 98

A device that measures turbidity

Front 99

Metabolic activity

Back 99

Assumes certain amounts of metabolic wastes are in direct proportion to the number of bacteria

CO2 and acid production are measured

Front 100

Dry weight

Back 100

Organisms are removed from media, filtered, and weighed

Good for filamentous bacteria that don't form colonies