Hi
The inhibition of spore germination and growth of Botrytis cinerea upon treatment with toxic molecule occured on solid culture medium (petri dishes) as predicted before. Strikingly, the spores germinated normally in liquid medium that contain also the toxic molecule at the same concentration (flasks).
How can we explain such observation??
(See attached pic.)
Your solution may be attributed to the nature of your toxic molecule. Whether it is a volatile or fixed compound.
I know there are metabolic pathway shifts in fungi when they are grown under those two conditions. The fungi may be inhibiting uptake of the inhibitor, inactivating the inhibitor or may just be insensitive to it under growing conditions as a submerged culture.
Thank your for your answer Muhammad Nadeem
So the toxic effect of the tested compound is inhibited in liquid culture?
Boredi Silas Chidi
The compound is the porphyrin tetrasulfonate and it is stable in the culture medium
Jay Sperry Thank you for your answer Mr. Sperry
Maybe secreted molecules/enzymes (antioxidants) by the fungi in liquid culture may lead to inhibition of toxicity or porphyrin uptake.
I agree with Jay's and Carlos's answers. Porphyrins bind metals, the properties of which are affected by redox status. Your liquid cultures seem deep (1 vol of medium:5 vol of flask), which may restrict oxygenation of the medium and thus the toxicity of a porphyrin metal complex. Solid media are more aerobic.
I prefer a 1:10 medium:flask volume ratio for liquid fungal cultures. Is porphyrin toxicity dependent on a trace metal's concentration (e.g. Fe, Zn etc.)? Use a defined inorganic medium to test (i.e. remove all metals, then supplement individually). Test redox effects with potassium ferrocyanide:ferricyanide (1:1; 0:1; 1:0) redox couple and uncouples.
t is possible that in a liquid medium, the conditions of aeration and the water activity, favor more the fungal growth, in addition the availability of the toxic remains in a diluted solution. The question would be: the concentration of the toxic used in the solid medium and in the liquid. Is it equivalent?
Stephen M Marek
Thank you for tour answer
The porphyrins (TPPS) are phototoxic also in their free base form (without metal complexation). Yes, maybe it concerns aeration as the flasks are deep and there will be not sufficient oxygen amount to induce porphyrin toxicity.
Beatriz elena Guerra
Thank you for your answer. What do you mean by "equivalent concentration in the 2 media" ??
This may be partly attributed to the differences in aeration and osmotic differences created by these two types of media due to their nature.
As Phil indicated it would be useful to know the type of toxic molecule. What I know is that the nature and type of media have an influence on the growth of a fungus. This is partly because, of aeration and the osmotic differences that exist in the medium. The osmotic differences will determine the rate at which the nutrients could be absorbed by the mycelia of the fungus whereas the aeration will determine the concentration of oxygen available to the fungus for cellular respiration. So the question is which of the two above Erlenmeyer/conical flask containing liquid medium and Petri plates with the solid medium will have adequate aeration and enhances ease of absorption of nutrients by the mycelia of the fungus? It will also be useful to know if the volume and concentration of the medium and the toxic molecule were the same for both media.
In addition, if the toxin is a highly volatile substance it could also be the reason why spore and growth inhibition might have occurred on solid culture because it remained and was not likely to evaporate and even if it does at a lower rate as compared to the liquid medium. Although the number of incubation days the cultures were exposed to could also be a possible reason.
These are my initial thoughts
THANK YOU
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