Hi, I ran a batch in 4 flasks starting 6 days ago, 2 heterotrophically and 2 mixotrophically. The 2 heterotrophic ones smell bad when I take samples everyday, and for some time, I think I smell the same thing in one mixotrophic culture. The smell reminds me of the E.coli cultures I used to grow, not in the current lab I am in but from a few years ago. I just remember that stinky smell.
To check for contamination, I examined the culture under microscope at 400X resolution, and I found nothing other than healthy algae cells. And yesterday I took one proteose agar plate that I use for the algae, and streaked onto it with one heterotrophic culture that I suspected of E.coli contamination. After incubating at 37C overnight, nothing showed up in the plate. But the smells are still there. I am kind of confused. I used glycerol and yeast to feed my algae. Can certain metabolites from algae cause the same stinking smells as the E.coli?
Some one please enlighten me on this. Thanks!
Could you please provide the recipes for the media (now and back then with E. coli) and the alga species?
may be short peptides from the utilization of yeast extract by algae were degrades and result the formation of stinking smell...... we can't still say that this is E.coli. contamination for confirming it you have to plate the sample on EMB agar media... and observe the typical morphology and color of colonies for E.Coli...
Please check for any contamination with any other algal culture which might be able to produce toxins as metabolites on utilizing the energy components
Thank you all for the advices, and sorry for my late response.
The media I am using for Chlorella culture is the basal medium (K2HPO4, KH2PO4, CaCl2, MgSO4, NaCl, FeSO4, VB1, and A5 solution), which is supplemented with glycerol and yeast extract. We ordered our strain from UTEX, and it's the only strain that is being used right now in our lab.
E.coli was like 5-6 years ago, when I was in another institute. The media I used then is the Luria-Bertani broth medium, which as I remember, contains only tryptone, NaCl and yeast extract.
Well, my dear freind, if I have to answer your question, then it is like this: The algal culture can not smell rose after all and the only smell it can have is a stink (call it E.coli smell)> No it is not like that, Just check that there could be some dead filaments and that is rotting.
Hi Zhang,
The moment you use something like an yeast extract in your media, its an invitation for bacterial growth.
First thing to do is to check for contamination on LB or EMB or etc agar plates.
Secondly, you have a basal salt medium so why not do a photoautotrophic growth with CO2 supply. During such a cultivation, bacterial contaminants that aren't symbionts wouldn't survive.
If you still fail to detect the contamination, one could always think of doing a 16s rRNA analysis.
There are several tricks for gaining an axenic culture, one of it being use of agar tubes. One could inoculate the culture deep into the agar and due to phototaxsis only agal cells would swim up to the surface.
Good luck
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