Hi!
I´m having a disagreement with my supervisor on the topic of ingestion of cholesterol by C.elegans.
My belief is that C.elegans ingest cholesterol directly from NGM. He believe that cholesterol is taken up by bacteria(OP50) from NGM-agar after 37 degrees over night on NGM-agar, then OP50 is ingested by C.elegans.
Who is right?
ummm. best not to argue with your supervisor too much, so try to break it to him gently. you are right. E. coli does not take up cholesterol.
see: Peripheral-Type Benzodiazepine Receptor Function - Endocrinology
endo.endojournals.org/content/139/12/4991.full.pdf
by H Li - 1998 - Cited by 240 - Related articles
3H-Cholesterol uptake by E. coli cells was examined using the indi- cated concentrations of control or IPTG-treated transformed bacteria incubated in the …
Thanks, for the articles. I’ve read the articles now but not sure where the evidence for my opinion is quoted.
Correct me if I’m wrong about the following:
Imu1: The article you refer to it state that E.coli does not have the receptor for uptake of cholesterol? The researches introduce it and then E.coli begins uptake of cholesterol. Does OP50 have this receptor?
SteveH: The article you refer to they use: Low-cholesterol enviroment = only NGM and High cholesterol enviroment = NGM + H3-labeled cholesterol? However the supplemented cholesterol is not taken up by the bacteria, but rather lie beside?
Does this mean that cholesterol from NGM will not be sufficient for growth and development of C.elegans?
He has given me this article as a support for his view: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC216971/
He is not easy to convince so any help i greeted. Thanks for the reply so far!
ok, fair enough. cholesterol can become incorporated into E. coli membranes even though they don’t have a genuine cholesterol transporter
(which would import cholesterol into the cytoplasm). note that Moreno et al. concluded that the amount
of cholesterol taken up by E. coli was overestimated by approx 5-fold by Eaton et al. http://link.springer.com/article/10.1007%2FBF01579549#page-1
But, whatever. You might as well do the damn experiment, since it is pretty easy. Grow E. coi cells in cholesterol-containing medium (to be fair, use the same concentration as in NGM, not some crazy high level), then wash and try growing worms on them on either cholesterol plus or cholesterol-free plates (no nutrients added; or use liquid).
my guess is that the worms won’t be happy without cholesterol in the medium, but hey i’ve been wrong before. that’s what makes science interesting 
ah you beat me to it. However;
The Eaton et al. paper quoted by your boss used cholesterol @ 20mg/L as opposed to the 5µg/L used in NGM plates (see the legend for Table 1.)
At that conc you’re going to get passive incorporation into the membrane.
As lmu1 pointed out (just seconds before I was poised for action), Eaton et al. were probably ~5-fold too optimistic about incorporation.
The Li et al. paper introduced the mouse peripheral-type benzodiazepine receptor into E.coli (which don’t have it) to study its kinetics.
The paper I suggested showed that cholesterol is taken up by C. elegans directly by the CUP-1 (now called ChUP-1)-mediated incorporation of cholesterol into vesicles (rather than indirectly via OP50 ingestion and catabolism).
Knocking this out (ChUP-1) makes the worms sick…take home message, they need cholesterol.
So, all of the evidence points to worms ingesting fluid from the NGM surface which contains cholesterol and incorporating the cholesterol into vesicles for further processing/transport.
Hope that clears things for you.
Regards
Steve
and if you need further reassurance…ammo…perspective etc., then read this;
http://www.jlr.org/content/45/11/2044.full.pdf+html
Steve
nice!