Hello everyone,
My work has the aim to assess the anthracene degrading potential by a strain, by using the colorimetric method with redox indicator 2,6-DCPIP.
The test of the biodegradability of anthracene showed a total discoloration of the DCPIP after only 20 min of incubation with the bacterial strain. The discoloration was observed also in the biotic control (BH medium + strain + DCPIP)
Do you have an idea about this issue?,Why does the DCPIP discolor quickly (20min) after adding the inoculum (in the assay and in the biotic control)?
Thank you!
Dear Bellebcir Anfel!
I've never come across the method you mentioned, so I can only speculate about this.
DCPIP is a non-specific redox indicator. It will respond to any change in redox potential, whether it be anthracene or any other substrate oxidation, or just a side redox reaction.
It is possible that the inoculum contains some impurities. Then you can try to wahs the cells (centrifuge and resusepend in 1% saline).
Or the microorganism itself accumulates nutrients, and metabolic redox reactions occur even without the introduction of a substrate.
I hope my guesses help you.
Regards
Dear all, it can be even faster (10min). Please have a look at the following RG document. My Regards
https://www.researchgate.net/publication/6121730_A_simple_and_highly_repeatable_colorimetric_toxicity_assay_method_using_26-dichlorophenolindophenol_as_the_redox_color_indicator_and_whole_eukaryote_cells
I generally agree with Kirill;
The 2,6-DCPIP is basically acting as an electron acceptor (turning from blue to clear in the process). I assume you see no reaction in the growth media without cells but do see one in the flasks with washed cells but no substrate. It is possible when you wash the cells that a small amount of anthracene (or whatever growth substrate you are using) is still present or that the cells have accumulated something like PHB (polyhydroxybutyrate) that can serve as a substrate when they are under starvation conditions. Maybe try re-adding oxidized 2,6-DCPIP to both live samples + substrate (cells + anthracene) and biotic controls (no substrate) after a few days to a week and see if the 2,6-DCPIP remains oxidized in the biotic controls but turns clear in the live + substrate. If that occurs, the cells have exhausted the unknown substrate, and you know this is probably what is going on.
Good Luck
Paul
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