Name: Lori
Status: Educator
Grade: 9-12
Location: LA
Country: United States
Date: December 2005
Question:
Hi
I am helping some students with science fair project. We need to
grow a culture of e coli in luria and transfer to nutrient agar
plates. Question? What process do I use to propagate the e coli in
luria? Do I just transfer a measured amount of bacteria and then let
grow? For how long will I have to let them grow before we can plate
on agar?
Thanks so much
Replies:
Assuming you have a 37 degree C incubator, inoculate the Luria broth
with an E. coli culture using a sterile pipet or inoculation loop.
Place the broth culture in the incubator for 24 hours. The culture
should be turbid (cloudy) and contain 10^8 and 10^9 cells/mL. At this
point, spread some of the culture on a nutrient agar plate and
inculate the plate for 24-48 hours at which time individual colonies
should be visible.
Ron Baker, Ph.D.
E coli has a generation time of about 20 minutes, so you will have a
good culture to work with by the next day. The broth should be cloudy
when you look at it. Then you can take a sterile loop, or sterile
cotton swab and transfer it to the nutrient agar. You can purchase
sterile swabs from a biological supply company such as Carolina, Ward'
or Fisher. Then you will need to grow the E coli on the nutrient agar
for another day. If you have an incubator, the bacteria will grow in
one day but if you need to grow them at room temp give them another
day.
Make sure that you have a way to dispose of the cultures properly-a
tub of 10% bleach works nicely. You should also decontaminate any
work surfaces with 10% bleach as well.
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