microbio more quiz ppt Flashcards
what agar will we be using
tryptic soy agar
what organisms will we be observing today
almonella typhimurium
Serratia marcescens
Shigella flexneri
Vibrio parahaemolytic
what temps are serratia marcescens gonna be held at
25 and 37 degrees celcius
2 types of media
Selective media and differential media
selective media
contains ingredients which are conducive to
some while inhibiting to others
differential media
contains ingredients with which the bacteria
interact in order to create a visual effect
mcconkey agar is both differential and selective media (t/f)
true ( another media is eosine methylene blue)
Differential properties means
how do different organisms appear on this medium
what agar should you know for today
Eosin Methylene Blue , Hektoen agar, MacConkey Agar, Mannitol salt agar
purpose of Eosin Methylene Blue
isolation of fecal coliforms
Mannitol salt agar concentration
(7.5-10 concentration)
Mannitol salt agar contains
alcohol mannitol and phenol red
organisms you will observe today pt 2
Eosin Methlyene Blue
- Escherichia coli
* Hektoen Agar
-Shigella flexneri
- Salmonella typhimurium
* MacConkey Agar
- Escherichia coli
Mannitol Salt Agar
- Staphylococcus aureus
- Staphylococcus epidermidis
what do we have to do to the plates from last lab
Re-streak Gram positive isolate
where did we draw sample from last class
river water
3 phases to find “Most Probable Number” of culiforms present in 100ml flask
presumptive, confirmed, , completed
presumptive phase
detects bacteria
confirmed phase
Confirms that the organisms producing gas are enteric organism
completed phase
Definitively confirm + BGLB test for coliform bacteria
.tubes are streaked onto Eosine Methylene Blue (EMB)
agar
in eosine methylene blue what do carbs do
encourage growth of fecal coliforms
Lactose
Sucrose
in eosine methylene blue what does Peptone do
promotes growth of m/o on media
what dyes are in eosine methylene blue
eosine y and methylene blue
how many colony forming units should each plate have in spread plates for viable ounts
30-300
Direct Counts use
Petroff-Hauser Chamber
what do we do to reduce concentration of bacteria in liquid
serial dilutions
direct count formula =
Number of cells/ml = # cells/sq. x (2x107) x dilution
i) the conversion factor _______ accounts for the area of the square
(2x107)
volume of liquid in which the bacteria are being counted
5x10-8 ml).
- Wash slides with____alcohol before returning them to the box
70%
viable count method formula
av. # cfu/plate x
(1/dilution) x (1/volume
plated)
