I have experienced a colour change from green to white in Trichoderma reesei and in some other organisms, despite the fact that I subcultured the organisms under the same conditions as the source organisms. Any idea why this happens? Also, is this colour change likely to affect the organisms' abilities to produce desired compounds such as enzymes?
Thank you.
Oh dear! A change from green to white at least in Trichoderma reesei is an almost certain sign it has lost its capacity to produce cellulases or whatever recombinant product it may be carrying e.g. under the cbh1 promoter. I have seen this phenomenon "too often" over the past 40 years. If you dlilute and plate onto e.g. potato dextrose agar you will almost certainly find that all white colonies are non-productive and oligosporous; possible green-sporulating colonies will probably have "original" properties. The characteristic yellow staining of the PD agar matrix will also follow the sporulation/non-sporulation division. At VTT the spores of a "healthy" (= sporulating) strain are preserved in glycerol suspension (20% in physiological saline + 250 ul/litre Tween 20) at -80oC in single-use aliquots - do not re-freeze! The next time a cultivation is planned, it is started off with the next aliquot...
Good luck, I've been there :)
Sporulation can cause colour change . Trichoderma cultures turn green with age as sporulation occurs. Prepare slides to observe
You say that you used 'the same conditions'. Does this mean that you also used exactly the same growth medium? A change in medium can trigger a different morphology and colour even when using exactly the same isolate/strain. A change to a different life stage phase, such as reproduction, could be a reason for the observed colour change, but if your colour change has happened with 'other organisms' also then I would strongly suspect either a common change in the growth medium or a chemical contaminant of some sort. I agree with Vikineswary Sabaratnam that you should microscopically examine the cultures and compare them with the original.
Some fungi tend to degenerate if they are transferred to often to new plates. This happens because they dont have to fear competition or lack of resources and so certain genes are switched off.This effects mainly the secondary metabolism (and of cause enzymes that are involved). Hence color changes can occur. If this happens I would advise to reactivate older strains from e.g. cryo conservation.
Oh dear! A change from green to white at least in Trichoderma reesei is an almost certain sign it has lost its capacity to produce cellulases or whatever recombinant product it may be carrying e.g. under the cbh1 promoter. I have seen this phenomenon "too often" over the past 40 years. If you dlilute and plate onto e.g. potato dextrose agar you will almost certainly find that all white colonies are non-productive and oligosporous; possible green-sporulating colonies will probably have "original" properties. The characteristic yellow staining of the PD agar matrix will also follow the sporulation/non-sporulation division. At VTT the spores of a "healthy" (= sporulating) strain are preserved in glycerol suspension (20% in physiological saline + 250 ul/litre Tween 20) at -80oC in single-use aliquots - do not re-freeze! The next time a cultivation is planned, it is started off with the next aliquot...
Good luck, I've been there :)
Very interesting to hear from you. Well in nature natural selection is continuously going on which is nothing but mutational effect to suit the dynamic nature of any environment. All that I can say now is: what you are observing is nothing but a well known phenomenon called as PHENOTYPIC LAG. It may or may not affect your other characateristics like certain enzyme production by the fungi.
I also did some sub-culturing and found colour changes as well. Sometimes it is a characteristic feature of using a particular media and at times it is interesting to note the diffusing pigments as it could be useful secondary metabolites. Should the metabolites colour appear different in each subculture, then it is likely a contamination.
Dear all, the same problem of th whitening of the colonies happened.
Anyone could cite a publication about this phenomena for Trichoderma? I would like to review this on my PhD thesis.
Thank you a lot for the information on this discussion list.
Cheers
I think Michael has already answered. Trichoderma is one such fungi which loses many biochemical activities when repeatedly subcultured on easily utilizable substrate and some of those genes are linked to the pigment producing genes. However, in case of Mary, I suspect that it is related to furfural production by Trichoderma reesei .
Even though this is coming a bit late, i genuinely appreciate the assistance with the comments, as they turned out to be helpful at the time. The isolate lost the enzyme producing abilities but i got another one. Thank you all
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