Microbial growth

Question 1

What are the two requirements for Microbial growth?

Answer 1

Physical and chemical requirements

Question 2

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

Answer 2

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

Question 3

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

Answer 3

Temperature
- psychrophile
- psychrotroph
- mesophile
- thermophile
- hyperthermophile

PH
- acidophiles
- neutrophiles
- Alkalophiles

Question 4

Temperature

Answer 4

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

Question 5

minimum temp

Answer 5

lowest temperature that can support growth of the microbe

Question 6

optimum temp

Answer 6

preferred temperature that best supports the growth of the microbe

Question 7

maximum temp

Answer 7

highest temperature supporting the growth of the microbe

Question 8

Name the different bacterial groups based on their range of temperature

Answer 8

Psychrophiles
Psychrotophs
Mesophiles
Thermophiles
Hyperthermophiles

Question 9

Psychrophiles

Answer 9

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!)

Question 10

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

Answer 10

Psychrophiles

Question 11

Psychrotrophs

Answer 11

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)

Question 12

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

Answer 12

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)

Question 13

Mesophiles

Answer 13

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

Question 14

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

Answer 14

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

Question 15

Thermophiles

Answer 15

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

Question 16

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

Answer 16

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

Question 17

Hyperthermophiles

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

(topic on food safety)

Answer 20

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

Question 21

Interpret the food-safety graph

Answer 21

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

Question 22

Explain the Freeze thaw cycle, and provide an example

Answer 22

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

Question 23

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

Answer 23

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

Question 24

Acidic substance pH

Answer 24

If the pH is below 7

Question 25

Neutral substance

Answer 25

If the pH is equal to 7

Question 26

Alkaline substance

Answer 26

If the pH is above 7

Question 27

Acidophiles

Answer 27

Bacteria that grow at a very low pH

Question 28

Alkalophiles

Answer 28

Bacteria that grow at a very high pH

Question 29

Neutrophiles

Answer 29

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

Question 30

What happens when milk becomes acidic?

Answer 30

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!

Question 31

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

Answer 31

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

Question 32

Saline solution

Answer 32

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

Question 33

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

Answer 33

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)

Question 34

Honey is an example of what type of solution

Answer 34

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

Question 35

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

Answer 35

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)

Question 36

Isotonic

Answer 36

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

Question 37

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

Answer 37

food preservation ex. salted fish and honey

Question 38

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

Answer 38

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

Question 39

extreme halophiles - provide an example where they can be found

Answer 39

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

Question 40

Blood salt concentration

Answer 40

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

Question 41

Name the different chemical requirements

Answer 41

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

Question 42

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

Answer 42

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

Question 43

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

Answer 43

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

Question 44

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

Answer 44

Nitrogen, Sulfur, Phosphorus and iron

Question 45

Trace elements importance and provide an example

Answer 45

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

Question 46

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

Answer 46

trace elements such as zinc and copper

Question 47

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

Answer 47

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

Question 48

Obligate aerobes

Answer 48

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

Question 49

Facultative anaerobes - name the two zones

Answer 49

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

Question 50

Obligate anaerobes

Answer 50

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

Question 51

Microaerophiles

Answer 51

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

Question 52

Aerotolerant Anaerobes

Answer 52

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

Question 53

Lactobaccillus is found where?

Answer 53

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

Question 54

Culture

Answer 54

Microbes that are continuously growing and multiplying in a medium

Question 55

Inoculum

Answer 55

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

Question 56

name the types of culture

Answer 56

Batch culture and continuous culture

Question 57

Batch culture

Answer 57

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

Question 58

Continous culture

Answer 58

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!)

Question 59

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?

Answer 59

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

Question 60

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?

Answer 60

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

Question 61

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

Answer 61

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

Question 62

What is the solidyfing agent in solid media

Answer 62

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

Question 63

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

Answer 63

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

Question 64

Chemically undefine media

Answer 64

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

Question 65

Chemically defined media

Answer 65

* All of the media components known * Referred to as a minimal media ex. media containing known quantities of salts and sugars

Question 66

Blood carying nutrients is an example of what type of media

Answer 66

undefined media

Question 67

Selective media

Answer 67

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

Question 68

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

Answer 68

Selective media

Question 69

Differential Media's purpose and provide an example

Answer 69

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

Question 70

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

Answer 70

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

Question 71

Mackonkey Agar is

Answer 71

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

Question 72

Selective portion of Mackonkey agar

Answer 72

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

Question 73

Differential portion of Mackonkey agar

Answer 73

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)

Question 74

Bacterial Growth refers to an increase in what

Answer 74

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

Question 75

Binary Fission

Answer 75

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

Question 76

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

Answer 76

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

Question 77

*E.coli* in rich media generation time

Answer 77

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

Question 78

*M. tuberculosis* generation time

Answer 78

has a very slow generation time of 24 hours

Question 79

Bacterial growth curve

Answer 79

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

Question 80

The Bacterial growth curve phases

Answer 80

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

Question 81

Lag phase

Answer 81

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

Question 82

Expontential phase

Answer 82

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

Question 83

Stationary phase

Answer 83

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

Question 84

Death phase

Answer 84

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

Question 85

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

Answer 85

The lag phase

Question 86

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

Answer 86

Exponential phase

Question 87

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

Answer 87

stationary phase

Question 88

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

Answer 88

Death phase

Question 89

Two primary ways that bacterial cells can be counted

Answer 89

Direct and viable count

Question 90

Direct count

Answer 90

- 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

Question 91

Viable count

Answer 91

– 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

Question 92

Each cell from the original dilution develops into a

Answer 92

single colony

Question 93

interpret viable count diagram

Answer 93

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

Question 94

Calculation of viable count

Answer 94

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

Question 95

cfu/ml

Answer 95

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