Transcript MICROBIOLOGY LECTURE TITLE: Measuring Bacterial Growth

Counting Bacteria
Serial Dilutions
Because of their very ______ ______,
counting the number of bacteria in a
sample can be _________
Although _______ _______ are possible
with a ______________, they require a
lot of time and ___________
Why Count the Number of
Bacteria??
• ________ _____________:
– How effective drugs are in killing
microorganisms?
• ___________________:
– How many MO in CSF, blood, urine
• ___________ ____________:
- Contaminants in food, milk,
water
Total Cell Count
• The most common method of
_______________ the total microbial
cells (______ ___ _________)
• The ______ ___________ of cell
suspension in a __________
_____________ of known _______
using a ________________
Total Cell Count – Both
living and dead MO
• Disadvantage:
____________________________________
____________________________________
____________________________________
• Advantage:
____________________________________
____________________________________
____________________________________
Total Cell Count – Both
living and dead MO
• Neubauer ___________ ___________
• Special _______ ____ _______
_______, microscopic marks on
slide, known _________
•
Counting Chamber
Counting Chamber
•Use special ______________ ____
_____________________
•Count specific areas of
__________________, multiply by
__________________ ______________
Instrumentation
• * _____________________ (Light Meter)
Each single ____ stops some ______
from
____________________________________________
•
One side _____ ________, then test
tube containing MO, other side _______
________________
•
Needle reading from scale, then
________________ _____________ telling # of
__________________________________________
•
Coulter Counter
• Another method for _____________
_____________
• An electronic instrument
“_____________ _________”
• Has a tiny tube (_____ ______
_____________) that lets through
only one cell at a time
Viable Cell Count –
Living Cells Only
Viable Count – Living
Cells only
An easier method is to ______
________ _____ __ _____ ______
(nutrient agar plate) and count the
number of ________ _____ ______
If the bacteria are ______ ____ ______,
each bacterial cell in the original sample
should produce a _______ _______
Serial Dilutions
Bacterial samples must be _______
considerably to obtain ___________
___________
To determine the ________ ___ ______
in a bacterial culture carry out _______
____________
Serial Dilutions
Bacterial cell numbers are usually _______
_____ _____________________________
Plating out this sample, undiluted, would lead
to the creation of a ___________________
Bacterial Lawn - many individual bacteria
colonies that are ______________________
____________________________________
Serial Dilutions
Bacterial cell numbers _____ __ __ _______
This is done by ______ ________ the amount
of bacteria you have in your sample
A ______ _________ of bacteria sample is
mixed with a _____ _______ (sterile broth or
water), and then _______ ___________ are
made
Serial Dilutions
A small amount of _____ ___ ____
_______ _________ ________ is then
spread onto an ______ ________
The numbers of bacterial colonies that
______________________________
Serial Dilutions
Work ___________ using multiplication
with the “___________ ____________”
________ ________ - the ______ ___
______ that you have diluted the bacteria
sample with the diluent solution
Make a determination of the numbers of
bacteria in ______ ________ _________.
Serial Dilution
Serial Dilutions
*Make ________ _____________
*Spread a small amount from
each tube onto _______ _______
*Culture bacteria for a ________ __
_________
*Count colonies
________________________________
Membrane Filtration
• ________ __________ can also be
used to determine the ________
_______________
• In this method ______ _____
___________ onto membrane filter
which is then placed over a
________ ______ __________.
Membrane Filtration
• The methodology is similar to
conventional _______ ________
_______________.
• Membranes have a printed
millimeter ________ and colonies
can be counted under a _________
_________________.
Factors essential for __________ ________
--proper ________________
--proper ___________________ (space,
temperature)
--No inhibiting factors
Factors that _____________________
__________________________________________
--lack of _____________
--lack of __________ __________________
--presence of an ___________ __________