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microbiology > Microbial growth > Flashcards

Microbial growth Flashcards

1
Q

What are the two requirements for Microbial growth?

A

Physical and chemical requirements

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2
Q

List the types of chemical requirements and the different microorganism types in the diff types of requirements)

A
  • carbon (heterotrophs and autotrophs)
  • oxygen (obligate aerobes, obligate anaerobes, facultative anaerobes, Aerotolerant anaerobes, microaerophiles)
  • nitrogen, sulfur, Phosphorous
    and iron
  • Trace elements (Zn and Cu)
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3
Q

What are the types of physical requirements for Microbial growth and list the type of microorganisms in each

A

Temperature
- psychrophile
- psychrotroph
- mesophile
- thermophile
- hyperthermophile

PH
- acidophiles
- neutrophiles
- Alkalophiles

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4
Q

Temperature

A

A type of Physical requirement
- each microbal species has a specific temp. range above and below which the microbe cannot grow/survive

This range usually spans 30oC
- Minimum: lowest temp. that can support growth of the microbe (below that temp, they are not dead, just asleep!)
-Opimum: preferred temp that best supports the growth of the microbe
- Maximum: highest temp supporting the growth of the microbe

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5
Q

minimum temp

A

lowest temperature that can support growth of the microbe

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6
Q

optimum temp

A

preferred temperature that best supports the growth of the microbe

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7
Q

maximum temp

A

highest temperature supporting the growth of the microbe

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8
Q

Name the different bacterial groups based on their range of temperature

A

Psychrophiles
Psychrotophs
Mesophiles
Thermophiles
Hyperthermophiles

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9
Q

Psychrophiles

A

Cold loving
temp range supporting growth -5°C to +15°C
killed at 20°C
found in the deep ocean and polar enviornments
No issues w/ food preservation (our body temp too high for them to survive too!)

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10
Q

What bacteria is found in the deep ocean and polar enviornments and is killed at 20°C

A

Psychrophiles

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11
Q

Psychrotrophs

A

Bacteria within this group have a very broad temp range
Temp range min (0), max (~35°C)
Optimal temp ~15-30°C (fastest growth occurs here)
These microbes will cause food to spoil in your fridge (even if put in fridge, theyre still growing and doubling- the fridge is good to protect from growth and spoilage)

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12
Q

you found spoiled food in your fridge, what type of bacterial group- based on their range of temp, caused this?

A

Psychotrophs (temp range min (0), max (~35°C), optimal temp (~15-30°C= fastest growth))
- they will grow in a refridgerator (will do so very slowly)

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13
Q

Mesophiles

A

love moderate temperatures (big concern b/c our body temp is the optimum range for growth)
- temp range ~10-45°C
- Optimum temp 30-37°C
- Most bacteria are mesophiles
- Most pathogens (disease causing microbes) have an optimal temp of 37°C
- Bacteria within this group are alive in your fridge but are not growing

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14
Q

What bacterial group (based on their range of temp) loves moderate temperatures, are alive in your fridge but not growing (unless taken out = start growing) and have the potential to live in your body

A

Mesophiles (temp range ~10-45°C, optimal temp 30-37°C)

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15
Q

Thermophiles

A

Temperature range ~45-70°C
Optimal range ~60°C
Cannot cause disease in the body

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16
Q

What bacterial group (based on their range of temperature) cannot cause disease in the human body

A

Thermophiles (temp range of 45-70°C, optimal temp of ~60°C

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17
Q

Hyperthermophiles

A

temp range 65-110°C
Bacteria within this group are limited to a very few places on earth where the water reaches such high temps
ex. deep ocean vents

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18
Q

What bacterial group (based on their temp. range) can survive such high temps and are found in deep ocean vents

A

Hyperthermophiles (temp. range 65-110°C)
- Bacteria within this group are limited to very few places on earth where the water reaches such high temperatures

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19
Q

Food safety involves the use of…?
- What is heat used to..? and cold temp is used too..?

A

the use of both hot and cold temperature in order to control bacterial populations (safe for food consumption)

heat is used to kill mesophiles and psychotrophs that are living on food products (ex. cooking)

Cold temps are used to slow the growth of microorganisms (cold = put them to sleep, dont have to worry about getting sick)
- only psychotrophs will grow in a refridgerator and will do so very slowly, all other microorganisms will not be able to grow

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20
Q

Cooking and pasteurization is an example of killing what type of bacterial groups based on their temperature range?

(topic on food safety)

A

Mesophiles and psychotrophs
- heat is used to kill these bacterial groups living on food products

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21
Q

Interpret the food-safety graph

A

Comparing the approximate temp range for Bacillus Cereus multiplying in rice

  • 5 hrs for red (43 C) = dangerous temps for 5 hrs, they double
  • could be a bug or pathogen that could be harmful when eaten in the rice

the middle of the graph = the temp u want to accelerate through

  • 2 hrs for blue Blue (15 C)= less than 2 hrs, time it takes to drop thru is less than 2 hrs
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22
Q

Explain the Freeze thaw cycle, and provide an example

A

crystals can poke holes in the cells
ex. if put in freezer, even if the temp doesn’t kill some cells, the crystals can kill = physical destruction, leaving only some left to survive

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23
Q

Ph is the measurement of..?
- Whats the scale range?
- Name the different types

A

is a measurement of the acidity and akalinity of a substance
- measured on a scale of 0-14
- if the pH is below 7 = acidic substance
- if pH is equal to 7 = neutral substance
- if pH is above 7 = alkaline substance

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24
Q

Acidic substance pH

A

If the pH is below 7

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25
Q

Neutral substance

A

If the pH is equal to 7

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26
Q

Alkaline substance

A

If the pH is above 7

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27
Q

Acidophiles

A

Bacteria that grow at a very low pH

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28
Q

Alkalophiles

A

Bacteria that grow at a very high pH

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29
Q

Neutrophiles

A

Bacteria that grow at pH values b/w 5 and 8
- optimum pH is ~7

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30
Q

What happens when milk becomes acidic?

A

Lactic acid is a waste product of milk - the protein in milk unfolds which forms chunks (and becomes sour) - b/c of the bacteria in there - they become acidic and die
- some bacteria have an optimum growth of pH if they move away from that optimum range, then this can affect them!

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31
Q

Define Osmosis and provide an example
- How does water move?
- What are the classifications of solutions

A

the movement of solvent molecules across a membrane or barrier of some sort
ex. movement of water across a plasma membrane

Water always moves from an area of low conc. to high conc. (concentration gradient)

All solutions can be classified as:
1) Hypertonic
2) Hypotonic
3) Isotonic

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32
Q

Saline solution

A

need to give patient an isotonic solution if youre building up their blood volume

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33
Q

Hypertonic solutions
- explain what happens if a cell is placed in a hypertonic solution

A

The solution is highly concentrated with solute
ex. solute = sugar or salt
when a cell is placed in a hypertonic solution, water will rush out of the cell (movement from low to high concentration)
= cell will shrivel or dry up! (plasmolysis)

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34
Q

Honey is an example of what type of solution

A

hypertonic solution b/c it has more solute in the solvent

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35
Q

Hypotonic solutions
- explain when a cell is placed in a hypotonic solution

A

the solution has a low concentration of solute
- when a cell is placed in a hypotonic solution, water will rush into the cell (movement from low to high concentration)
- the cell will burst

(the cell wall is a counter pressure, the cell will lyse due to the water)

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36
Q

Isotonic

A

When two solutions are of equal concentration
- placing them into a solution that is of equal concentration will not result in any net movement of water

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37
Q

Osmotic pressure is important in…?
- and provide an example

A

food preservation
ex. salted fish and honey

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38
Q

Bacteria that have high [NaCl] require what percentage..?
- what would you call these bacteria and provide an example where they would be found

A

some bacteria have adapted to life in very high salt concentrations requiring as high as 30% NaCl
- these bacteria are referred to as extreme halophiles
- ex. bacteria that live in the dead sea

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39
Q

extreme halophiles
- provide an example where they can be found

A

Bacteria that adapted to life in very high salt concentrations (high as 30% NaCl) ex. bacteria that live in the dead sea

40
Q

Blood salt concentration

A

~0.9%
- salt concentration is too low to inhibit the growth of most microorganisms

41
Q

Name the different chemical requirements

A
  1. Carbon
  2. Nitrogen, Sulfur, Phosphorus and Iron
  3. Trace elements
  4. Oxygen
42
Q

Carbon
- name the two organisms that need carbon and their differences in obtaining carbon

A

A chemical requirement
- the backbone of all living matter: required for organic molecules

Heterotrophs: obtain their carbon from organic matter ex. sugars, proteins and lipids

Autotrophs: obtain their carbon from inorganic matter
ex. CO2

43
Q

Nitrogen, Sulfur and Phosphorus and Iron importance
- What is it used for?
- Provide an example

A

required in smaller amount then carbon (taking them away = cells not going to be okay)
- used for synthesis of cellular material, enzyme function etc.
ex. Protein, nucleic acid, ATP

44
Q

What is required in smaller amount then carbon (taking them away = cells not going to be okay)
- used for synthesis of cellular material, enzyme function etc.
ex. Protein, nucleic acid, ATP

A

Nitrogen, Sulfur, Phosphorus and iron

45
Q

Trace elements importance and provide an example

A

Need them! if missing = dietary insufficiency
- required in extremely small amounts
- ex. Zinc (+ve charge deals w/ opposite charge, enzymes and proteins cannot fold properly if not present) and Copper
- essential to the function of certain enzymes

46
Q

essential to the function of certain enzymes, need them! if missing = dietary insufficiency, and they are required in small amounts

A

trace elements such as zinc and copper

47
Q

Oxygen
- name the different classes of microorganisms based on oxygen tolerance

A

this is only required by some organisms
can be extremely toxic to some organisms
- there are 5 classes of microorganisms based on oxygen use tolerance
1. Obligate aerobes
2. facultative anaerobes
3. Obligate anaerobes
4. microaerophiles
5. Aerotolerant anaerobes

48
Q

Obligate aerobes

A

require O2 for cellular respiration (obligation to be w/ O2) ex. humans

49
Q

Facultative anaerobes
- name the two zones

A

can use O2 for cellular respiration but can also grow well in anaerobic enviornments
- contains Oxic zone (O2) and anoxic zone (no O2): competition for O2 at the top

50
Q

Obligate anaerobes

A

cannot use O2 for cellular respiration and are killed in the presence of O2 (obligation to be away from O2)

51
Q

Microaerophiles

A

(small O2 friend)
- require O2 in very low amounts and are killed by higher (go where O2 is just enough)

52
Q

Aerotolerant Anaerobes

A

Cannot use O2 for cellular respiration but are not killed by its presence

53
Q

Lactobaccillus is found where?

A

can be found in vagina (cant use O2 and they make acid)
- pH of vag is 4.5 = defense against sexually transmitted disease - action = acidifaction can be helped by aerotolerant anaerobes - they both coexist in the vagina

54
Q

Culture

A

Microbes that are continuously growing and multiplying in a medium

55
Q

Inoculum

A

Microbes introduced into a culture (innoculation) ex. Koch’s postulates experiment - innoculating

56
Q

name the types of culture

A

Batch culture and continuous culture

57
Q

Batch culture

A

liquid media
- once started there are no further nutrients added
- once the nutrients are used up the bacteria begin to die
- the amount of nutrients is the limiting component

58
Q

Continous culture

A

Open system
-Nutrients are continually added
-Wastes are continuously removed
-This type of system supports indefinite growth
(you can also add a buffer=a mix of acid and base, to keep them growing and healthy!)

59
Q

You are put into a locked room with other people with just food, no washroom and the wastes accumulates while the nutrients deplete what type of culture is being represented in this analogy?

A

Batch culture because you have a liquid media, once started there are no further nutrients added and the nutrients are used up = bacteria begin to die
- the amount of nutrients is the limiting component

60
Q

You are put into a locked room with other people and the room is constantly being cleaned, continuously fed and this supports indefinite growth (give them enough of what it is that they need), what type of culture is being represented in this anaolgy?

A

Continuous culture
- it is an open system
- nutrients are continuously added
- wastes are continuously removed
- this type of system supports indefinite growth!

61
Q

Explain the purpose of Solid Media
- What is it
- What is it made out of?

A

Allows growth of colonies
-densely packed groups of cells

allows the isolation of pure cultures
- One cell reproduces and eventually forms a huge population of cells which are genetically identical to one another

the solid media contain all of the nutrients required by the cells
- in addition to nutrients the solid media contains agar which is a solidifying agent
- polysaccaride derive from marine algae
- cannot be degraded by most bacteria

62
Q

What is the solidyfing agent in solid media

A

Agar
- polysaccaride from marine algae
- cannot be degraded by most bacteria

63
Q

Culture medium
- What is it?
- What are the types of culture medium

A

nutrients prepared for microbial growth
- allows us to grow pure bacterial cultures in the lab

medium can be chemically defined or chemically undefined
- Prior to innoculaion the media must be sterile (containing no living microbes)

two types of media
1) Chemically undefined media
2) Chemically defined media

64
Q

Chemically undefine media

A

contains unknown components
referred to as complex media
ex. media containing yeast extract. All of the soluble components com from crushed yeast cells

65
Q

Chemically defined media

A
  • All of the media components known
  • Referred to as a minimal media
    ex. media containing known quantities of salts and sugars
66
Q

Blood carying nutrients is an example of what type of media

A

undefined media

67
Q

Selective media

A

used to suppress the growth of unwanted organisms
-promotes the growth of desired bacteria and an example

Example: Bismuth Sulfite Agar used to culture Salmonella typhi
-Inhibits the growth of gram positive and most other gram-negative bacteria

68
Q

Bismuth Sulfite Agar used to culture Salmonella typhi Inhibits the growth of gram positive and most other gram-negative bacteria is an example of

A

Selective media

69
Q

Differential Media’s purpose and provide an example

A

Used to distinguish in between different types of bacteria
-All types of bacteria are able to grow but colonies of certain bacteria look different on the plate

Example: Blood Agar plates used to culture Streptococcus
pyogenes and other bacteria that lyse and eat red blood cells

70
Q

blood Agar plates used to culture Streptococcus
pyogenes and other bacteria that lyse and eat red blood cells is an example of

A

Differential media
- used to distinguish diff types of bacteria
- all types of bacteria are able to grow but colonies of certain bacteria look different on the plate

71
Q

Mackonkey Agar is

A

Both selective and differential

Selective: Bile salts and dyes in the media inhibit the growth of most non-intestinal bacteria, promoting the growth of bacteria that live in the intestine

Differential: Lactose fermentation: bacteria that ferment lactose sugar produce acid products that turn the pH indicator pink
- Example: E.coli
Lactose non-fermenters appear white
- Example: most intestinal pathogens

72
Q

Selective portion of Mackonkey agar

A

Contains bile salts and dyes
- therefore inhibits growth of non-intestinal organism and promotes growth of intestinal organisms

73
Q

Differential portion of Mackonkey agar

A

Involves lactose fermentation
-Bacteria that ferment lactose sugar, produce acid products = turn pH indicator pink

Differentiate:
1. lactose fermenters = pink
2. non lactose fermenters = white (ex. most intestinal pathogens, like e.coli)

74
Q

Bacterial Growth refers to an increase in what

A

Refers to an increase in bacterial cell number and not an increase in bacterial cell size

75
Q

Binary Fission

A

how most bacteria reproduce

  1. The bacterial cell elongates and
    makes an identical duplicate of its
    chromosome
  2. The bacterial cell containing two
    chromosomes continues to grow
    and a cross-wall forms in between the
    two chromosomes
  3. The two cells separate and you have
    the original parent cell and a new
    genetically identicle daughter cell
76
Q

Generation time
- define
- What is the variation gen. time in diff bacteria

A

Measuring the growth of bacteria = the calculation of the generation time of a particular organism
- The generation time is the time it takes for a bacterial population to double in size

Generation time varies in between different bacteria
Most bacteria have a generation time in between 1-3 hours
- E.coli in rich media has a extremely short generation time of 20 minutes
- M. tuberculosis has a very slow generation time of 24 hours

77
Q

E.coli in rich media generation time

A

short gen. time of 20 minutes
- nutrient rich medium has many factors that detemine how quickly the bacteria is able to grow.
- ex) how much sleep we get, what we eat

78
Q

M. tuberculosis generation time

A

has a very slow generation time of 24 hours

79
Q

Bacterial growth curve

A

Since bacteria grow exponentially the bacterial growth curve is constructed using the log of the cell number

80
Q

The Bacterial growth curve phases

A
  1. Lag Phase:
    -A period of adaptation
    -Cells are adjusting to the new
    media and preparing for growth
  2. Exponential Phase (log phase):
    -Cell numbers are increasing
    exponentially
    -A period of maximal reproduction
    -This is the phase used to calculate
    the growth rate
  3. Stationary Phase:
    -Cells have reached the maximum
    population density
    -Nutrients have been depleted
    -Growth rate= death rate
    -There is not an increase in cell number
  4. Death Phase:
    -All nutrients are exhausted
    -Toxic waste products have accumulated
    -Death rate exceeds growth rate
81
Q

Lag phase

A

-A period of adaptation
-Cells are adjusting to the new
media and preparing for growth

82
Q

Expontential phase

A

aka log phase
-Cell numbers are increasing exponentially
-A period of maximal reproduction
-This is the phase used to calculate
the growth rate

83
Q

Stationary phase

A

-Cells have reached the maximum
population density
-There is not an increase in cell number
-Nutrients have been depleted
-Growth rate= death rate

84
Q

Death phase

A

-All nutrients are exhausted
-Toxic waste products have accumulated
-Death rate exceeds growth rate

85
Q

The phase of the bacterial growth curve that’s a A period of adaptation, Cells are adjusting to the new media and are preparing for growth

A

The lag phase

86
Q

The phase of the bacterial growth curve where cell numbers are increasing exponentially, is a period of maximal reproduction, and is used to calculate the growth rate

A

Exponential phase

87
Q

The phase of the bacterial growth curve where cells have reached the maximum population density, Nutrients have been depleted, Growth rate= death rate, there is not an increase in cell number

A

stationary phase

88
Q

The phase in the bacterial growth curve where all nutrients are exhausted, toxic waste products have accumulated and death rate exceeds growth rate, you can also find endospores in this phase too

A

Death phase

89
Q

Two primary ways that bacterial cells can be counted

A

Direct and viable count

90
Q

Direct count

A
  • Cells are counted using a light microscope
    – Usually takes place in a special
    counting chamber
    – This type of count is very inaccurate
    because it counts both live and
    dead cells
91
Q

Viable count

A

– Only live cells are counted
– A liquid culture is diluted (1 ml)
– Dilutions are plated onto agar plates
– Plates are incubated until the colonies grow
Calculation of viable count: number of colonies on plat x reciprocal of dilution of sample = cfu/ml

Steps (extra info)
Place 1 ml into the original inoculum and there’s 9ml in each tube
= diluting 1 to 10, 1 to 1000, 1 to 10000, etc./tube
- then plating it out
keep doing this and the growth gets less and less
- then you count how many are present and multiply them by the number of CFUs by dilution factor

92
Q

Each cell from the original dilution develops into a

A

single colony

93
Q

interpret viable count diagram

A

Each cell from the original dilution
develops into a single colony
- The number of colonies is then counted and can be used to determine the number of bacteria that were present in the original sample

The counts are expressed as colony-forming units per mL (cfu/mL)
- The assumption is that 1 cfu= 1 bacterial cell

94
Q

Calculation of viable count

A

number of colonies on plate x reciprocal of dilution of sample = number of bacteria / mL (cfu/mL)

95
Q

cfu/ml

A

expressed as:
“colony forming units per mL”
- the assumption that 1 cfu = 1 bacterial cell

microbiology (6 decks)

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