Flashcards in Lecture 5 Deck (98):
Each microbial species has a specific..
temperature range, above and below which the microbe cannot grow/survive
The temperature rang usually spans..
30 degrees C
lowest temp that can support growth of the microbe
preferred temp that best support the growth of microbe
Human body temp is usually
37 degrees C
highest temp supporting the growth of the microbe
5 groupings of bacteria based on their range of temperature
cold loving, temp range supporting growth -5 to 15 C. Killed at 20 C. found in deep ocean and polar environment. no issues w/ food preservation
bacteria w/in this group have very broad temp range 0 to 35 C. optimal temp 15 to 30 C. these microbes will cause food to spoil in fridge
temp range 10 to 45C optical temp is 30 to 37C. alive in fridge but not growing
Most bacteria are what temperature range
Most pathogens (disease causing microbes) have an optimal temp of
temp range 45 to 70C. optimal temp 60C. cannot cause disease in human body
temp range 65 to 110C. bacteria in this group are limited to very few places on Earth were water reaches such high temp (deep ocean vents)
Heat is used to kill _____ and _____ living on food products (ex: cooking)
mesophiles and psychrotrophs
Cold temperature are used to.......
slow growth go microorganisms
What type of bacteria can grow in fridge
measurement of acidity and alkalinity of substance
What pH allows cell to fold
Most bacteria grow at or around a ___ pH
bacteria that grow at very low pH
bacteria that grow at very high pH
bacteria that grow at pH values between 5 and 8
movement go solvent molecules across a membrane or barrier of some sort
Water ALWAYS moves from an area of..
low concentration to and area of high concentration (up the concentration gradient)
solution is highly concentrated w/ solute
When cell is placed in hypertonic solution water will..
rush out of cell from low to high concentration, cell will shrivel or dry up
solution has a low concentration of solute
When a cell is placed in hypotonic solution water will...
rush into cell from low to high concentration, cell will burst and be unfixable
when 2 solutions are of equal concentration, no result of net movement when placed into isotonic solution
Osmotic pressure is very important for
bacteria adapted to life at high salt concentration. bacteria live in dead sea (30% NaCl)
Blood salt concentration
0.9%, salt concentration too low to inhibit growth of most microorganism
backbone of all living matter
obtain their carbon from organic matter, so unable to create their own (ex:proteins)
obtain their carbon from inorganic mater (ex: CO2)
Nitrogen, sulfur, phosphorus, and iron
required in smaller amounts then carbon
nitrogenous bases, protein amino acids
certain amino acids
nitrogenous bases and ATP
ETC and hemoglobin
required in extremely small amounts, essential to the function of certain enzymes (ex: zinc)
only required by some organisms, can be extremely toxic to some organisms
5 classes of microorganisms based on oxygen use tolerance
require oxygen for cellular respiration
can use oxygen for cellular respiration but can also grow well in anaerobic environments
cannot use oxygen for cellular respiration and are killed in presence of oxygen
cannot use oxygen for cellular respiration but aren't killed in its presence
require oxygen in very low amounts and are killed by higher concentrations
microbes that are continuously growing and multiplying
microbes introduced into a culture
liquid media, once started there are no further nutrients added, once nutrients used up the bacteria begin to die
What is limiting component for batch culture
amount of nutrients
open system, nutrients are continually added. wastes are continuously removed
What type of system supports indefinite growth
allows growth of colonies, contains all n nutrients required by the cells, contains agar
densely packed groups of cells
solidifying agent, polysaccharide derived from marine algae, cannot be degraded by most bacteria
Solid media allows
isolation of pure cultures
For solid media one cell reproduces and eventually forms..
a huge population of cells which are genetically identical to one another
nutrients prepared for microbial growth, can be chemically defined or undefined
Cultire medium allows us to ..
grow pure bacterial cultures in lab
Prior to inoculation the media must be..
sterile, containing no living microbes
Chemically undefined media
contains unknown components, referred to as complex media
Example of chemically undefined media
media containing yeast extract, all of the soluble components come from crushed yeast cells
Chemically defined media
all of the media components are known, referred to as a minimal media
Example of chemically defined media
media containing known quantities of salts and sugars
used to suppress the growth of unwanted organisms, promotes the growth of desired bacteria
Example of selective media..
bismuth sulfite agar used to culture salmonella typhi
used to distinguish in between diff types of bacteria, all types of bacteria are able yo grow but colonies of certain bacteria look diff on the plate
Example of differential media...
blood agar plates used to culture streptococcus pygoenes and other bacteria that lyse and eat red blood cells
Example of agar both selective and differential
How MacConkey agar is 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
How MacConkey agar is differential
lactose fermentation, lactose non-fermenters appear white
bacteria that ferment lactose sugar produce acid products that turn pH indicator pink (E.coli)
Bacterial growth refers to an..
increase in bacterial cell number and not an increase in bacterial cell size, most bacteria reproduce by binary fission
First step in binary fission
bacterial cell elongates and makes identical duplicate of its chromosome
Second step in binary fission
bacterial cell containing two chromosomes continues to grow and a cross walk forms in between the two chromosomes
Third step in binary fission
the two cells separate and you have the original parent cell and a new genetically identical daughter cell
measuring the growth of bacteria allows the calculations of the generation time of a particular organism
The generation time is the time it takes for...
a bacterial population
Generation time varies in between..
Most bacterias generation time is
between 1 - 3 hours
E.coli in rich media has extremely short generation time of
M. tuberculosis has a very slow generation of
Since bacteria grow exponentially the bacterial growth curve is constructed using ..
log of the cell number
period of adaptation, cells adjusting to the new media and preparing for growth
Exponential phase (log)
cell numbers are increasing exponentially, period of maximal reproduction, used to calculate growth rate
cells reached max population density, nutrients have been depleted, growth rate = death rate (no increase)
all nutrients are exhausted, toxic waste products have accumulated, death rates exceed growth rate
2 primary ways that bacterial cells can be counted
cells are counted using a light microscope, usually takes place in special counting chamber
Direct count is very inaccurate because..
it counts both live and dead cells
only live cells are counted, liquid culture diluted, dilutions are plated onto agar plates, plates are incubated until the colonies grow
First step in counting bacteria
Each cell from the original dilute develops into a single colony
Second step in counting bacteria
number of colonies are then counted and can be used to determine the number of bacteria that were present in original sample
The counts are expressed as..
colony forming units per mL (cfu/mL)