The bacterial strain I was working on showed activity. I ran out of crude so I cultured a new batch and this one showed no activity. I'm hoping there was no human error involved. Any ideas on what may have caused this?
may be it get some contamination which you didn't notice... or could be that the production of that active metabolite is related to a special phase of growth of the bacteria and you cultivated your bacteria in the wrong time...but I think to repeat your culture again with fresh inoculum and the same condition and using the same chemical .. and hope for the best :)
was the bioassay used to determine the activity run in duplicate? It could be a false positive, but assuming it is not:
This happens in our lab sometimes, as Ghada said, give it one more try. However there are a lot of pathways that can be turned on and/or off with very little modifications (different room temperature, light condition, flask size/shape, and even oxygen and carbon level). If the extract of the second try is still inactive I would say drop the strain and move on to the next one instead of trying to figure out why it lost activity.
sometimes the secondary metabolism changes when you repeat the cultivation of the bacteria as it's highly affected with any small change in culturing condition. So, you should compare the chemical profiles of both extracts to figure out what were the metabolites responsible for the activity.
I had faced similar problem several times but I got succeed in it. You don't worry it happens in this field. First retrieve the strain from the mother culture and culture it from the same media which you used for the secondary metabolites production. Extract the metabolites from the strain at different stages like every 6 hour interval and check for activity.
Thank you all for your answers. I altered my culturing method so instead of storing the strains in a -70 freezer and reviving them, I just kept them in the incubator and revived them and the result was that the activity was duplicated. Thanks again.
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