Microbiology Chapter 4

Question 1

What are three general reasons to grow microbes in culture?

Answer 1

Medical significance, nutritional uses, industrial uses.

Question 1

What is German physician Robert Koch famous for?

Answer 1

Studied disease causing bacteria; Nobel prize. Helped understand cholera epidemic in India. Developed methods of cultivating bacteria.

Question 2

__________ is the time it takes for the population of bacteria to double.

Answer 2

Generation Time

Question 3

Generation time varies among what two conditions?

Answer 3

Species and environmental conditions.

Question 4

________ is defined as an increase in the number of cells in a population.

Answer 4

Microbial Growth

Question 5

How do the growing conditions in nature differ from the growing conditions in the laboratory?

Answer 5

Nature has changing/complex conditions.

Question 6

What is the name for polymer-encased communities that bacteria grow in?

Answer 6

Biofilm

Question 7

What are examples of biofilm in our daily lives?

Answer 7

Slippery rocks in stream.
Slimy gunk in sink drains,
Scum in toilet bowl.
Dental plaque.

Question 8

Describe the formation and structure of biofilm.

Answer 8

Free cells adhere to surface and multiply. Release polymers to which cells attach and grow. Extra polymeric substances (EPS) give slimy appearance. Nutrients and wastes pass through characteristic channels, cells communicate via chemical signals.

Question 9

What are two helpful aspects of biofilms?

Answer 9

Bioremediation and Wastewater Treatment

Question 10

What are some negative implications of biofilms?

Answer 10

Most infections involve biofilms, as they are often resistant to immune system and antibiotics. Accumulations in drains and pipes are most resistant to disinfectants. Leads to decay/disease (from dental plaque).

Question 11

What is the term for a population of cells derived from a single cell that allows the study of a single species?

Answer 11

Pure Culture

Question 12

What percent of microorganisms can be cultured?

Answer 12

1%

Question 13

What technique is used to obtain pure culture?

Answer 13

Aseptic Technique

Question 14

Behavior of microbes is dependent on _______.

Answer 14

Environment/where they are grown.
(Nature vs. Laboratory)

Question 15

In the laboratory, how are cells grown?

Answer 15

Grown in or on culture medium. Contains nutrients dissolved in water. Can be liquid broth or solid gel.

Question 16

With correct conditions in laboratory, single cell will multiply to form what?

Answer 16

Colony (Approximately 1 million cells easily visible).

Question 17

What ingredient is used to solidify medium?

Answer 17

Agar

Question 18

What are the benefits of using agar to solidify medium?

Answer 18

Few microbes can degrade it. Not destroyed by high temperatures and can be sterilized.

Question 19

What is a closed system?

Answer 19

Culture in which nutrients are not added, nor are wastes removed.

Question 20

Characteristic ______ seen in closed broth culture.

Answer 20

Growth Curve

Question 21

Describe the lag phase of bacterial growth.

Answer 21

Number of cells does not increase. Cells begin synthesizing enzymes required for growth. Delay depends on conditions.

Question 22

Describe the exponential phase of bacterial growth.

Answer 22

Cells divide at constant rate. Generation time measured. Most sensitive to antibiotics.

Question 23

What are two byproducts of the exponential growth phase?

Answer 23

Primary metabolites such as amino acids.
Secondary metabolites such as antibiotics are produced as nutrients are depleted and wastes accumulate.

Question 24

Describe the stationary phase of bacterial growth.

Answer 24

Nutrient levels too low to sustain growth. Growth rate = death rate. Continue to produce secondary metabolites.

Question 25

Describe the death phase of bacterial growth.

Answer 25

Total number of viable cells decreases. Cells die at constant rate. Exponential, but usually much slower than cell growth.

Question 26

Describe the phase of prolonged decline of bacterial growth.

Answer 26

Some fraction may survive. Adapted to tolerate worsened conditions.

Question 27

Describe how cell growth can vary in the middle of the colony vs. on the edge.

Answer 27

Edge has little competition for oxygen and nutrients. Center has depleted oxygen and nutrients, and accumulation of potentially toxic wastes. Can be in different growth phases (edge can be in exponential growth while center is in death phase).

Question 28

What are the four major factors that affect microbial growth?

Answer 28

Temperature, atmosphere, pH, and water availability.

Question 29

What is the name for the type of bacteria that live in harsh environments? What domain are they from?

Answer 29

Extremophiles. Archaea.

Question 30

Temperature range and significance for Psychrophiles.

Answer 30

5 to 15 degrees Celsius. Found in Arctic and Antarctic regions.

Question 31

Temperature range and significance of Psychrotrophs.

Answer 31

15 to 30 degrees Celsius. Important in spoilage of refrigerated foods.

Question 32

Temperature range and significance of Mesophiles.

Answer 32

25 to 45 degrees Celsius. Pathogens thrive in 35 to 40 degrees Celsius.

Question 33

Temperature range and significance of Thermophiles.

Answer 33

45 to 70 degrees Celsius. Common in hot springs and compost heaps.

Question 34

Temperature range and significance of Hyperthermophiles.

Answer 34

70 degrees Celsius or greater. Usually archaeal, found in hydrothermal vents.

Question 35

How do thermophiles remain stable under high temperatures?

Answer 35

Proteins of thermophiles resist denaturing. Stability comes from amino acid sequence.

Question 36

How does refrigeration slow spoilage of food?

Answer 36

Limits growth of otherwise fast growing Mesophiles. Psychrophiles and psychrotrophs can still grow, but slowly.

Question 37

T/F: Freezing preserves food and is effective at killing microbes.

Answer 37

False, freezing is not effective at killing microbes.

Question 38

Describe the oxygen requirements of obligate aerobes.

Answer 38

Require O2.

Question 39

Describe the oxygen requirements of facultative aerobes.

Answer 39

Use O2, but don't require it.

Question 40

Describe the oxygen requirements of obligate anaerobes.

Answer 40

Cannot use O2.

Question 41

Describe the oxygen requirements of microaerophiles.

Answer 41

Require small amounts of O2 only.

Question 42

Describe the oxygen requirements of aerotolerant anaerobes.

Answer 42

Obligate fermenters (can grow in O2, but they don't use it).

Question 43

What is a Reactive Oxygen Species (ROS)? What are the two byproducts and why are they dangerous? How do organisms protect against this?

Answer 43

Harmful by-products of using O2 in aerobic respiration. Superoxide and hydrogen peroxide. Damaging to cellular components, cells must have protective mechanisms (produce enzyme superoxide dimutase that inactivates superoxide, also produce catalase).

Question 44

What is the one group that does not have protective mechanisms against the harmful byproducts of aerobic respiration?

Answer 44

Obligate anaerobes

Question 45

What group does not produce catalase?

Answer 45

Aerotolerant anaerobes

Question 46

How do bacteria respond to changes in environment?

Answer 46

Pump out protons if in acidic environment. Bring in protons if in basic environment.

Question 47

What bacterial group grows optimally at pH below 5.5?

Answer 47

Acidophiles

Question 48

What bacterial group grows optimally at pH above 8.5?

Answer 48

Alkaliphiles

Question 49

Most microbes are _______ and have an optimum pH range of 5 to 8.

Answer 49

Neutrophiles

Question 50

What two ingredients make water unavailable to cells, hence their use in food preservation?

Answer 50

Dissolved salts and sugars.

Question 51

What is the name for the type of bacteria that does not require high salt concentrations, but can withstand them?

Answer 51

Halotolerant

Question 52

What is the name for the type of bacteria that requires high salt concentrations?

Answer 52

Halophiles

Question 53

What are the (10) major nutritional elements for microbial growth?

Answer 53

Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium, and iron.

Question 54

What are the (5) trace nutritional elements for microbial growth?

Answer 54

Cobalt, zinc, copper, molybdenum, and manganese.

Question 55

What process converts inorganic carbon to organic carbon?

Answer 55

Carbon Fixation

Question 56

_________ use organic carbon vs. ________ use inorganic carbon.

Answer 56

Heterotrophs; Autotrophs

Question 57

What process converts N2 gas to ammonia then incorporating it into organic compounds? (converts it into a usable form for plants)

Answer 57

Nitrogen Fixation

Question 58

Nitrogen is required in bacteria for ______ and _____.

Answer 58

Nucleic acids and amino acids.

Question 59

What two nutrients are often limiting for bacteria?

Answer 59

Phosphorus and Iron.

Question 60

What are organic molecules that an organism cannot synthesize, as they must be present in the environment?

Answer 60

Growth Factors

Question 61

________ obtain energy from sunlight. List 3 examples.

Answer 61

Phototrophs. Plants, algae, photosynthetic bacteria.

Question 62

_______ obtain energy from chemicals. List examples.

Answer 62

Chemotrophs. Animal cells, fungi, many types of prokaryotes.

Question 63

What are the three most common sources of chemical energy for cells?

Answer 63

Sugar, amino acids, and fatty acids.

Question 64

Some prokaryotes extract energy from ________, such as hydrogen sulfide and hydrogen gas.

Answer 64

Inorganic Compounds

Question 65

T/F: Direct cell count counts both living and dead cells.

Answer 65

True

Question 66

Viable cell counts refer to _______?

Answer 66

Cells capable of multiplying