Lecture 6 - Microbial Growth Flashcards
Binary Fission
bacterial cell division/reproduction
Generation Time
the length of time it takes for 1 round of binary fission
Generation Time of E. coli
20 min
Who discovered biofilms?
Anton van Leeuwenhoek
Plaque that grows on teeth is an example of a ________.
Biofilm
Quorum Sensing
refers to how bacteria communicate with eachother and coordinate behavior (incl. use of nutrients) within the matrix of the biofilm
A microbe in a biofilm is ____ times more resistant to antimicrobials than microbes not in biofilms.
1000
Which endospore microbe caused food poisoning and tragically killed several at a dinner party?
Clostridum botulinum
4 Factors Influencing the Growth of Microbes
- Temp
- pH
- Osmolarity (tonicity)
- Salinity
Salinity
concentration of salt in a solution
Microbe that Causes Botulism
Clostridium botulinum
What can survive the high temps of canning?
Endospores
Dented or bloated cans of canned food could be indicative of possible ____________.
Botulism
Should canned foods be stored in hot areas?
No.
Temperature can affect a microbe’s _______.
Rate of Growth
*Note: different types of microbes grow faster at different temperatures depending on the type
Psychrophiles
microbes found in very cold/polar regions
(peak rate of growth at ~10 C)
Room Temp in degrees Celsius
~20
Body Temp in degrees Celsius
37
Psychotrophs
microbes that grow well at cooler temps and room temp and are primarily responsible for spoiling food
(peak rate of growth around room temp 20 C)
Mesophiles
microbes that grow well between 10-50 C
(mesophiles grow particularly well at body temp of 37 C)
Thermophiles
microbes that grow well in the heat
Extreme Thermophiles
microbes that grow well in extreme heat near boiling
-phile
loving; likes
alkalin
basic
(pH greater than 7)
acidophile
acid loving bacteria which grow well in acid environents with a pH less than 7
neutrophiles
bacteria that grow best in environments closer to a neutral pH of 7
alkalinophiles
bacteria that grow best in basic environments with pH greater than 7
buffers
maintain pH of a culture
Peptone
A cheap, rough buffer made from dehydrated animal protein that has been digested w/ enzymes
Na2HPO4
disodium phosphate
used as a buffer
KH2PO4
monopotassium phosphate
used as a buffer
halophiles
GreatSaltLake&DeadSea
microbes that like salty environments
-static or -stasis
stop/stand still
-cidal
to kill
Microbial Growth
an increase in the number of cells
Does Clostridium botulinum prefer environments with high or low oxygen concentration?
Low Oxygen
Acidic foods generally taste ___.
sour
Basic foods generally taste ____.
bitter
Why does “salting” help preserve food?
Salting creates an extremely hypertonic environment which draws the water out of and consequently kills the microbes
the tonicity of an environment affects _____.
osmotic pressure
What is the maximum percent of agar you can have in a culture medium?
1.5%
(No more than 1.5 g of agar per 100 mL of solution)
OBLIGATE Halophiles
REQUIRE environments with a high salt concentration
FACULTATIVE Halophiles
microbes that can withstand an environment with high salt concentrations but do not require the salt to survive
Why do microbes need Carbon and Oxygen?
all organic compounds require C & H
Why do microbes need nitrogen?
Nitrogen is found in nucleic acids such as DNA, RNA, ATP.
Nitrogen is part of chlorophyll in photosynthetic microbes.
Why do microbes need sulfur?
Sulfur is required make certain amino acids for proteins, vitamins and lipids.
Why do microbes need phosphorus?
Phosphorus is found in nucleic acids such as DNA, RNA & ATP.
Phosphorus is needed to make phospholipids and form the cell membrane.
Do all microbes require oxygen?
No. Only microbes that do aerobic cellular respiration and need the oxygen to act as the terminal electron acceptor.
Why do microbes need trace elements such as K, Fe, Mg, Ca, Zn?
to act as enzyme cofactors
SOD
Superoxide Dismutase
Function of SOD?
Superoxide Dismutase is an enzyme to neutralize potentially toxic forms of oxygen.
Name 3 Obligate Aerobes
- Bacillus pseudomonas
- Bacillus aeruginosa
- Mycobacterium tuberculosis
Name one genus of Obligate Anaerobes
Clostridium
Do obligate anaerobes produce catalase?
No
Do obligate anaerobes produce SOD?
No
Name two types of Facultative Anaerobes
- E. Coli
- Salmonella
Name genus of Aerotolerant Anaerobes
Lactobacillus
Name a type of Microaerophile
Listeria monocytogenes
Is Listeria Gram-Positive or Gram-Negative?
Gram-Positive
How many flagella does listeria have?
one
(monotrichous)
What type of infection is flu?
a respiratory infection
Gastroenteritis is often referred to as “the Stomach Flu” but is it a flu?
No, because flu is a respiratory infection and not a GI infection.
Common Symptoms of Gastroenteritis
diarrhea, stomach cramps, nausea, vomiting
turbidity
cloudiness seen in culture mediums that are growing bacteria
Microaerophile
requires oxygen but only in low concentrations
Agar
Made from red algae/red seaweed and is often used in culture mediums and used to create semi-solid surface for microbes to grow on.
inoculum
the microbes placed in a medium to grow
inoculate
the act of placing inoculum in a growth medium
Slant
When agar is used in a test tube rather than a plate and is allowed to solidify at an angle within the test tube
Why not use jello and gelatin instead of agar?
- Gelatin liquifies at a lower temp.
- Gelatin is easily broken down by enzymes produced by the bacteria.
Difference between a Chemically-Defined and a Complex Medium
Chemically defined mediums are expensive and the exact chemical composition of the medium is known in order to grow specific microbes.
Meanwhile Complex Mediums Are cheaper and the chemical composition varies between batches. Complex Mediums are more generic and are used to grow a variety of microbes.
Selective Medium
Medium containing inhibitory ingredients to prevent the growth of unwanted microbes but allows the growth of desired microbes
Common Method to Make a Medium Selective
add antibiotics to the medium
Differential Medium
make it easier to distinguish colonies of different organisms on the plate
Blood Agar is a commonly used ______ Medium.
Differential
Blood Agar is often used to distinguish hemolytic and non-hemolytic colonies of what type of bacteria?
Streptococcus
Group A Streptococci are hemolytic or non-hemolytic?
Hemolytic
Name 3 illnesses Streptococcus pyrogenes can cause
- Strep Throat
- Impetigo
- Necrotizing Fasciitis
Is MacConkey Agar a differential or selective medium?
Both
What is the purpose of the Streak Plate Method when inoculating a plate?
the purpose is to ultimately end up with colonies composed of only one species that originated from a single microbe.
Should you freeze your cultured plate to preserve the microbes?
No, because freezing will cause water crystals to form inside the microbes and will destroy them from the inside out.
Although, Deep Freezing with liquid nitrogen can be a long-term storage method.
Lyophilization AKA
Freeze-Drying
What are the 4 Phases of Microbial Growth?
- Lag Phase
- Log Phase
- Stationary Phase
- Death Phase
Lag Phase
Microbes are getting ready to divide but population growth has not yet occurred
Log Phase
exponential growth of microbes as the population increases
Stationary Phase
Nutrient in the medium are being used up and the rate of growth is the same as the rate of microbe deaths so the overall population of microbes remains approximately the same
Death Phase
nutrients are used up and microbes are dying off
If a microbe is viable, it is _____.
Living
What method would you use to determine the number of viable (living) cells in a culture)
Plate Count or Serial Dilution
What method would you use to determine the total number of cells in a culture?
Filtration and Direct Microscopic Count
When doing a Serial Dilution, which plate would you use to determine the number of microbes?
The plate with 30-300 colonies
(If multiple plates have 30-300 colonies, use the one as closest to 300)
Coulter Counters
Direct Electronic Counting of microbes in a suspension
Spectrophotometers
Measures the amount of light passing through a tube with microbes growing in it versus a tube with no microbes (the blank). The more microbes in the tube, the less light will pass through.
