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Microbiology > Unit 3 > Flashcards

Unit 3 Flashcards

1
Q

What are the 2 levels of bacterial growth

A

Cellular growth

Replication

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2
Q

Cellular growth of bacteria

A

Increasing mass at the cellular level (in preparation to divide)

Makes new cell components (proteins, cytoplasm, cell wall, DNA)

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3
Q

Replication in bacterial growth

A

Increasing mass at the population level

The number is cells increase exponentially due to binary fission

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4
Q

Binary fission

A

How bacteria replicate: one bacteria divides into 2 identical daughter cells

2 stages:
Replication of cellular components

Separation into two equal and identical halves by forming a septum in the middle of the cell

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5
Q

Generation time (AKA doubling time)

A

Time required for one round of binary fission (amount of time to double the number of bacteria)

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6
Q

What does the generation time depend on

A

Environment: growth factors, temp, oxygen, nutrients etc

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7
Q

Exponential (log) growth

A

The number of bacteria or population size doubles every generation

Equation:

N(total)=(Ni) 2^n

N= population 
n= generation
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8
Q

Bacterial growth curve is observed when

A

Microorganisms are grown in a culture in a closed system (limited space and nutrients)

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9
Q

What are the 4 phases of the bacterial growth curve

A

Lag phase

Exponential/log phase

Stationary phase

Senescence/death phase

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10
Q

What is the lag phase

A

Period of adjustments after cells are inoculated into fresh media

Very slow growth

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11
Q

What happens during the lag phase

A

Cells adapt to new conditions
Cells repair, and replenish spent materials
Increase in size due to synthesis of DNA and proteins
Minimal cell division

Varies in length (short, long or absent)

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12
Q

What is the exponential phase?

AKA log or logarithmic phase

A

Bacteria have acclimated and conditions are now optimal for growth (excess nutrients, space, lack of toxins)

Rapid growth (consistently doubles)

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13
Q

Why is the log phase clinically significant? (2)

A

Population is most uniform (chemical and physical properties): best time to identify bacteria

Bacteria in this phase are MOST susceptible to antibiotics

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14
Q

Why are bacteria most susceptible to antibiotics during the log phase

A

Because antibiotics often target a stage in binary fission

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15
Q

What is the stationary phase

A

Rate of replication equals rate of death

Overall number of bacteria stays constant

Occurs when growing conditions are no longer ideal

Less susceptible to antibiotics here

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16
Q

What is the senescence/death phase

A

Rate of cell death exceed rate of growth

Rapid decline in numbers of viable bacteria

Majority of cells die by autolysis

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17
Q

Autolysis

A

Expression of specific self-digestion Genes

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18
Q

Dormancy (metabolically inactive) bacteria is a response to what

A

Potential or actual change in environment, when it becomes unfavourable

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19
Q

What makes an environment unfavourable

A 
Lack of nutrients 
Lack of spaces
Increased waste 
Change in oxygen 
Change in temp
Presence of antibiotics
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20
Q

Examples of dormant states of bacteria

A

Persister cells

Endospores

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21
Q

What are persister cells

A

Small number of cells in a population that are slow or non growing

When environmental conditions improve, they reestablish population/reinfect

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22
Q

Persister cells are more ____ to kill with antibiotics

A

Difficult

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23
Q

Persister cells hide out in macrophages, and can survive through antibiotic treatment, to

A

Re infect

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24
Q

What are endospores

A

A dormant, tough, non reproductive structure in bacteria (gram positive)

Production Triggered by lack of nutrients (starvation)

Resistant to dry conditions/heat

Difficult to eliminate

Bacillus and clostridium produce these

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25
Q

Why is it important to know which phase of growth bacteria are in?

A

Bacteria can be identified best in the log phase

Bacteria are most vulnerable to harm in the log phase

Cells are more difficult to treat and identify in stationary phase

Stages of growth correspond to stages of infection

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26
Q

Physical and chemical requirements for growth

A 
Temperature
Oxygen levels
PH 
Moisture 
Osmotic pressure
Space
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27
Q

Temperate affects

A

Rate and amount of growth

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28
Q

Minimum temperature

A

Lowest temperature that growth will occurs

Less than minimum will inhibit growth

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29
Q

Optimal temperature

A

Growth is maximal

Ex. Incubator temperatures

30
Q

Maximum temperature

A

Highest temperature at which growth will occur

If exceeded, denaturation will occur

31
Q

Most clinically relevant species are mesophiles, their range of temperature is

A

20-45 degrees Celsius

32
Q

Fever

A

A Mechanism the body uses to decrease microbial growth during infection

33
Q

The ability to withstand low and high temperatures would be considered a

A

Pathogenic factor

34
Q

Ideal temperatures for: psychrophile

A

0-20 degrees Celsius

35
Q

Ideal temperatures for: psychrotrophs

A

0-30 degrees Celsius

15 degrees is optimal

36
Q

Ideal temperatures for: mesophile

A

20-45 degrees Celsius

37
Q

Ideal temperatures for: thermophiles

A

45-85 degrees Celsius

38
Q

Ideal temperatures for: thermoduric

A

Able to withstand high temp but do not grow at them, can survive pasteurization, including spores

39
Q

Bacteria require certain amounts of oxygen for growth depending on

A

The type of metabolic enzymes they express

40
Q

Bacteria that produce energy via oxidative phosphorylation and the electron transport chain

A

Require oxygen

41
Q

Bacteria that produce energy via fermentation

A

Do not require oxygen

42
Q

Aerobes

A

Grown in 21% oxygen

43
Q

Obligate aerobes

A

Can’t grow without oxygen

44
Q

Facultative anaerobe

A

Grown best in aerobic conditions but can grow in absence of oxygen

(Intestinal bacteria)

45
Q

Obligate anaerobe

A

Cannot grow if exposed to oxygen

46
Q

Microaerophile

A

Grow in 2-10% oxygen

47
Q

Some bacteria can alter their environments pH, how does E. Coli do this

A

Frequent cause of UTIs

Produces urease: an enzyme that converts urea to ammonia and CO2 to bring urine closer to ideal pH

Urine is slightly acidic, E.Coli has an optimal growth at pH of 7

48
Q

Optimal pH range for: acidophils

A

pH 4 (0-5.5)

49
Q

Optimal pH range for: neutrophils

A

pH 7.2 (5.5-8.5)

50
Q

Optimal pH range for: alkaliphils

A

pH 9 (8.5-11.5)

51
Q

Bacteria are made up of 70% water

So moisture is

A

Necessary for growth

52
Q

Osmotic pressure is

A

Difference in solute concentration between the inside of the bacteria cell and external environment

53
Q

Isotonic

A

No water movement

54
Q

Hypotonic

A

Less solutes outside the cell, more solutes inside the cell

Water moves into the cell, cell swells and bursts (lysis due to osmotic pressure)

Cell wall protects from osmotic lysis

55
Q

Hypertonic

A

Water moves out of the cell causing shrinkage (dehydration) (plasmolysis)

More solutes outside the cell

56
Q

Why do bacteria need room to grow?

A

Space allows toxic metabolic waste to diffuse out

57
Q

Normal intestinal flora are important in maintaining health by

A

Occupying space and preventing pathogenic bacteria from finding space to grow

58
Q

Metabolism: catabolism

A

Process of energy production

Energy is released by breaking down large molecules into smaller ones

59
Q

Metabolism: anabolism

A

Energy requiring processes

Energy is used to build molecules for growth and repair

60
Q

Heterotrophs

A

An organism that eats other plants or organisms for energy

Require pre-formed organic matter for energy and carbon needs (must be supplied)

61
Q

Why are bacteria more versatile than mammals in terms of nutrition?

A

Bacteria can utilize a wider range of nutrients including inorganic sources of carbon and other elements

62
Q

Macronutrients

A

Nutritional elements required in relatively large amounts by all living organisms

63
Q

Main macronutrients

A

Carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus

64
Q

True or false

Some bacteria can obtain carbon, nitrogen and sulfur from inorganic sources

A

True

65
Q

Other macronutrients need in lesser amounts

A

Potassium, calcium, sodium, magnesium, iron

Needed for proper function of enzymes and to maintain osmolarity

66
Q

Micronutrients

AKA trace elements

A

Only very small amounts required

Involved as co-factors in enzyme function and protein structure

67
Q

Examples of micronutrients

A

Manganese, zinc, Cobalt, Molybdenum, nickel, copper

68
Q

Essential nutrients are

A

Any nutritional component that has to be provided to the cell/organism because it is unable to produce it on its own

Usually taken from the host

69
Q

Bacteria have Different nutritional requirements based on the

A

Metabolic enzymes they have genes for

70
Q

Why must you know nutritional differences when growing bacteria in vitro

A

Can use to differentiate between different species

Microbiology (12 decks)

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