In serial dilution and spotting assay using yeast (for any particular growth defect phenotype) we see that, at times there is considerable growth at lower dilutions (high cell density) and growth defect phenotype in higher dilutions (low cell density). Why does the phenotype not show up in lower dilution spots?
thanks
Hi there,
This is the principle of dilution spot assay : in lower dilution the cell density is such that you can't make any difference as very little growth is needed to get a continuous layer of cells whereas at higher dilution you actually observe isolated clones growth which is easily related to clone diameter.
Also, when checking for auxotrophies, at lower dilutions the nutrients oozing out of dead cells can complement the nutritional deficiencies of their neighboring survivors. Or, if checking for antibiotic resistance, at low dilutions the antibiotic may get locally titrated out to a level that the survivors can withstand.
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