Microbial growth Flashcards
What are the two requirements for Microbial growth?
Physical and chemical requirements
List the types of chemical requirements and the different microorganism types in the diff types of requirements)
- carbon (heterotrophs and autotrophs)
- oxygen (obligate aerobes, obligate anaerobes, facultative anaerobes, Aerotolerant anaerobes, microaerophiles)
- nitrogen, sulfur, Phosphorous
and iron - Trace elements (Zn and Cu)
What are the types of physical requirements for Microbial growth and list the type of microorganisms in each
Temperature
- psychrophile
- psychrotroph
- mesophile
- thermophile
- hyperthermophile
PH
- acidophiles
- neutrophiles
- Alkalophiles
Temperature
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
minimum temp
lowest temperature that can support growth of the microbe
optimum temp
preferred temperature that best supports the growth of the microbe
maximum temp
highest temperature supporting the growth of the microbe
Name the different bacterial groups based on their range of temperature
Psychrophiles
Psychrotophs
Mesophiles
Thermophiles
Hyperthermophiles
Psychrophiles
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!)
What bacteria is found in the deep ocean and polar enviornments and is killed at 20°C
Psychrophiles
Psychrotrophs
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)
you found spoiled food in your fridge, what type of bacterial group- based on their range of temp, caused this?
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)
Mesophiles
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
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
Mesophiles (temp range ~10-45°C, optimal temp 30-37°C)
Thermophiles
Temperature range ~45-70°C
Optimal range ~60°C
Cannot cause disease in the body
What bacterial group (based on their range of temperature) cannot cause disease in the human body
Thermophiles (temp range of 45-70°C, optimal temp of ~60°C
Hyperthermophiles
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
What bacterial group (based on their temp. range) can survive such high temps and are found in deep ocean vents
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
Food safety involves the use of…?
- What is heat used to..? and cold temp is used too..?
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
Cooking and pasteurization is an example of killing what type of bacterial groups based on their temperature range?
(topic on food safety)
Mesophiles and psychotrophs
- heat is used to kill these bacterial groups living on food products
Interpret the food-safety graph
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
Explain the Freeze thaw cycle, and provide an example
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
Ph is the measurement of..?
- Whats the scale range?
- Name the different types
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
Acidic substance pH
If the pH is below 7
Neutral substance
If the pH is equal to 7
Alkaline substance
If the pH is above 7
Acidophiles
Bacteria that grow at a very low pH
Alkalophiles
Bacteria that grow at a very high pH
Neutrophiles
Bacteria that grow at pH values b/w 5 and 8
- optimum pH is ~7
What happens when milk becomes acidic?
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!
Define Osmosis and provide an example
- How does water move?
- What are the classifications of solutions
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
Saline solution
need to give patient an isotonic solution if youre building up their blood volume
Hypertonic solutions
- explain what happens if a cell is placed in a hypertonic solution
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)
Honey is an example of what type of solution
hypertonic solution b/c it has more solute in the solvent
Hypotonic solutions
- explain when a cell is placed in a hypotonic solution
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)
Isotonic
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
Osmotic pressure is important in…?
- and provide an example
food preservation
ex. salted fish and honey
Bacteria that have high [NaCl] require what percentage..?
- what would you call these bacteria and provide an example where they would be found
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
extreme halophiles
- provide an example where they can be found
Bacteria that adapted to life in very high salt concentrations (high as 30% NaCl) ex. bacteria that live in the dead sea
Blood salt concentration
~0.9%
- salt concentration is too low to inhibit the growth of most microorganisms
Name the different chemical requirements
- Carbon
- Nitrogen, Sulfur, Phosphorus and Iron
- Trace elements
- Oxygen
Carbon
- name the two organisms that need carbon and their differences in obtaining carbon
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
Nitrogen, Sulfur and Phosphorus and Iron importance
- What is it used for?
- Provide an example
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
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
Nitrogen, Sulfur, Phosphorus and iron
Trace elements importance and provide an example
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
essential to the function of certain enzymes, need them! if missing = dietary insufficiency, and they are required in small amounts
trace elements such as zinc and copper
Oxygen
- name the different classes of microorganisms based on oxygen tolerance
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
Obligate aerobes
require O2 for cellular respiration (obligation to be w/ O2) ex. humans
Facultative anaerobes
- name the two zones
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
Obligate anaerobes
cannot use O2 for cellular respiration and are killed in the presence of O2 (obligation to be away from O2)
Microaerophiles
(small O2 friend)
- require O2 in very low amounts and are killed by higher (go where O2 is just enough)
Aerotolerant Anaerobes
Cannot use O2 for cellular respiration but are not killed by its presence
Lactobaccillus is found where?
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
Culture
Microbes that are continuously growing and multiplying in a medium
Inoculum
Microbes introduced into a culture (innoculation) ex. Koch’s postulates experiment - innoculating
name the types of culture
Batch culture and continuous culture
Batch culture
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
Continous culture
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!)
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?
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
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?
Continuous culture
- it is an open system
- nutrients are continuously added
- wastes are continuously removed
- this type of system supports indefinite growth!
Explain the purpose of Solid Media
- What is it
- What is it made out of?
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
What is the solidyfing agent in solid media
Agar
- polysaccaride from marine algae
- cannot be degraded by most bacteria
Culture medium
- What is it?
- What are the types of culture medium
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
Chemically undefine media
contains unknown components
referred to as complex media
ex. media containing yeast extract. All of the soluble components com from crushed yeast cells
Chemically defined media
- All of the media components known
- Referred to as a minimal media
ex. media containing known quantities of salts and sugars
Blood carying nutrients is an example of what type of media
undefined media
Selective media
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
Bismuth Sulfite Agar used to culture Salmonella typhi Inhibits the growth of gram positive and most other gram-negative bacteria is an example of
Selective media
Differential Media’s purpose and provide an example
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
blood Agar plates used to culture Streptococcus
pyogenes and other bacteria that lyse and eat red blood cells is an example of
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
Mackonkey Agar is
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
Selective portion of Mackonkey agar
Contains bile salts and dyes
- therefore inhibits growth of non-intestinal organism and promotes growth of intestinal organisms
Differential portion of Mackonkey agar
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)
Bacterial Growth refers to an increase in what
Refers to an increase in bacterial cell number and not an increase in bacterial cell size
Binary Fission
how most bacteria reproduce
- The bacterial cell elongates and
makes an identical duplicate of its
chromosome - The bacterial cell containing two
chromosomes continues to grow
and a cross-wall forms in between the
two chromosomes - The two cells separate and you have
the original parent cell and a new
genetically identicle daughter cell
Generation time
- define
- What is the variation gen. time in diff bacteria
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
E.coli in rich media generation time
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
M. tuberculosis generation time
has a very slow generation time of 24 hours
Bacterial growth curve
Since bacteria grow exponentially the bacterial growth curve is constructed using the log of the cell number
The Bacterial growth curve phases
- Lag Phase:
-A period of adaptation
-Cells are adjusting to the new
media and preparing for growth - Exponential Phase (log phase):
-Cell numbers are increasing
exponentially
-A period of maximal reproduction
-This is the phase used to calculate
the growth rate - 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 - Death Phase:
-All nutrients are exhausted
-Toxic waste products have accumulated
-Death rate exceeds growth rate
Lag phase
-A period of adaptation
-Cells are adjusting to the new
media and preparing for growth
Expontential phase
aka log phase
-Cell numbers are increasing exponentially
-A period of maximal reproduction
-This is the phase used to calculate
the growth rate
Stationary phase
-Cells have reached the maximum
population density
-There is not an increase in cell number
-Nutrients have been depleted
-Growth rate= death rate
Death phase
-All nutrients are exhausted
-Toxic waste products have accumulated
-Death rate exceeds growth rate
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
The lag phase
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
Exponential phase
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
stationary phase
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
Death phase
Two primary ways that bacterial cells can be counted
Direct and viable count
Direct count
- 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
Viable count
– 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
Each cell from the original dilution develops into a
single colony
interpret viable count diagram
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
Calculation of viable count
number of colonies on plate x reciprocal of dilution of sample = number of bacteria / mL (cfu/mL)
cfu/ml
expressed as:
“colony forming units per mL”
- the assumption that 1 cfu = 1 bacterial cell
