Bacterial Growth Flashcards
What is the Gram morphology of Listeria monocytogenes?
G+ bacilli
What are the four physical factors that affect bacterial growth?
- Temperature
- pH
- Osmotic pressure
- Gas
What is the difference between psychrotrophs and mesophiles?
Psychrotrophs can withstand 20-30°C meanwhile mesophiles can withstand 25-45°C
The range of pH which human pathogens can withstand is:
5-8
Obligate halophiles require ____ salt concentrations
high
Facultative halophiles tolerate salt concentration within the range of:
2-15%
What is the main virulence factor of L. monocytogenes?
Listeriolysin breaks open vacuoles containing bacteria (ex: macrophages), releasing bacteria into the cytoplasm & preventing destruction by lysosomes. This allows the bacteria to access the cell’s actin.
Obligate aerobes only grow ___ the presence of oxygen
with
Two chemical factors that affect bacterial growth are:
- Sources of C, N, O, S, P + trace elements
- Sources of organic growth factors
An environmental factor that affects bacterial growth is:
Evasive defense mechanisms that require antibiotics to penetrate the membrane in order to be effective
L. monocytogenes grows best in 20-30ºC, which means it is a _____________.
psychrotroph
What are some reasons why L. monocytogenes is such a good food pathogen?
- Can grow in wide temp (3-42ºC) & pH range.
- Can survive in freezer temperatures.
- Can grow in high concentrations of NaCl (food preservation agent).
What is L. monocytogenes’ normal habitat?
Grasses & soil in the environment.
How does L. monocytogenes make its way into our food?
Food that has been contaminated with animal feces.
What are some symptoms of listeriosis from L. monocytogenes in animals?
CNS infection (“circling disease”) & septic abortion.
Define generation time
The time for one bacterium to divide into two
What are the four phases of bacterial growth kinetics
Lag phase, log phase, stationary phase and death phase
Describe the lag phase
There is minimal/no cell division
Describe the log phase:
The cell begins to divide; most metabolically active phase
Describe the stationary phase:
Cell division slows down
When culturing bacteria, a ___ ___ ___ is required, which can be solid, semi-solid or liquid
sterile nutrient material
Biofilms are:
Dynamic communities of bacteria which antibiotics are ineffective towards
The purpose of differential media when culturing bacteria is:
To identify/narrow down similar bacteria
Define anabolism
A chemical reaction that form complex organic compounds and require energy
