Estimating Bacterial Count Flashcards
computation of CFU
colony forming unit
represent particular cell that have dividing capabilities
colony forming unit
unit that we use for estimating the number of viable bacteria or the fungal cells in a sample
colony forming unit
asexual reproduction by a separation of the body into two new bodies
binary fission
– viable cells being computed utilizing hemocytometer
direct count
increase in the number of cells
microbial growth
Depends on the nutrients of culture medium and the environmental requirements of the microorganisms
microbial growth
parts of a growth curve
lag phase
log (exponential) phase
stationary phase
death (decline) phase
introduction of microorganism to the culture medium
lag phase
– phase where microorganisms increasese
exponential phase (log)
phase where microorganisms reach their carrying capacity
stationary phase
natural occurrence where organisms fight for limited resources
competition
– represent that resources on the environment has been depleted
death phase
general media used previously in midterms
nutrient agar
time of gearing up for division following change in culture conditions
lag phase
Introduction of microbes in the environment
lag phase
division at a constant rate (exponential)
log or exponential phase
death rate = birth rate
stationary phase
Represents the carrying capacity of the environment
stationary phase
Shows the max number of microbes
stationary phase
– constant per-capita death rate (exponential
death phase
Represents the competition
death phase
used to determine how microorganisms grow, assess the foods and monitor industrial processes
microbial counts
An indicator of spoilage
microbial counts
process through which the concentration of an organisms (ex. Bacteria) is systematically reduced through successive resuspension in fixed volumes of liquid diluent.
serial dilution
Usually the volume of __ is a multiple of 10 to facilitate logarithmic reduction of the sample organism
diluent
a substance used to dilute something.
diluent
counting methods (3)
direct count
pour plate method (viable count)
spread plate method (viable count)
counting methods for viable counting
pour plate method
spread plate method
– include microscopic counts using a hemocytometer or a counting chamber
direct count
Dead cells are also counted
direct count
technique when counting for direct count
L rule
The central square is further subdivided into 0.05 x 0.05 mm (0.0025 mm2) squares.
nunbauer ruling
is a tool used for manual cell countin
hemocytometer
what quadrants are counted in hemocytometer
1, 5, 13, 21,25
formula for direct count
cells/mm^2
number of cells in 5 squares * 5
formula for direct count
cells/mm^3
cells/mm^2 *10
cells / ml formula
cells /mm^3 x 1000
dilution factor in computation
10^4
formula for direct counting
(number of cells in 5 squares)(10)(1000)(DF)
method used in cell culture to determine the number of living cells in a culture
viable count/plate count
This is different from other cell counting techniques because it makes a distinction between live and dead cells
viable count/plate count
Colony forming units are only considered
viable count
consist of diluting a sample with sterile saline or phosphate buffer diluent until the bacteria are dilute enough to count accurately
standard plate count method
– should have between 30 and 300 colonies
final plates
– not acceptable for statistical reasons
<30
<30 means
too few to count
colonies too close to each other to be distinguished as distinct colony forming units
> 300
TNTC means
Too numerous to count
view different number of colonies in ppt
+1
an equipment that is designed to assist you when counting colonies on agar plates
colony counter
colony counting can be done via (3)
pushbutton
pen probe
needle probe
To look through the viewing area to assist with the counting of smaller colonies
magnifying glass
A glass viewing area with a grid pattern drawn on it and a light to illuminate the agar plate.
ruled counting area
pour plate method amount of innoculum
1.0ml
spread plate method amount of innoculum
0.1mL
formula for viable counting
(no of colonies)(total dilution factor)/volume of culture plated in ml
what part of the growth curve represent the increase in population of certain organisms
log (exponential) phase
loss of resources in a culture media
what part of a growth curve
stationary phase or death (decline) phase
which represents competition among organisms in growth chart
stationary phase
