Dear Doris et al.,
Here are some possibilities.
1. Larger colonies will appear in areas of the plate with fewer cells. This
could be competition for nutrients or reaction to waste products coming from
other colonies (Does anyone know what these waste products are? Doesn't
2. If your strain is very slow growing because of a particular mutation,
derivatives carrying suppressor mutations may catch your eye.
3. I don't know about S. cerevisiae, but S. pombe throws off diploid
strains. Some mutations increase this frequency. The haploids and diploids
could grow at different rates.
Try restreaking both large and small colonies to see if one size is stable.
That one might carry a supressor if choice 2 is responsible.
"I'd rather be fission."
Let's say you stick out a strain for single colony on a plate. What
would be your explanation (beside contamination of two strains) for
heterogenous colony size on a plate?
Trescowthick Research Laboratories
Peter MacCallum Cancer Institute
Locked Bag 1
Melbourne VIC 3000