by Stan Zahler
When you streak out Your Favorite Bacterium on an appropriate agar plate, the colonies reach an expected diameter and stop growing. Why?
Corollary: If you inoculate YFB in the center of an agar plate and incubate it, it would reach its expected diameter. What do you predict would happen if you touch the tip of a sterile hair to the edge of the colony, draw it out on the agar radially, and re-incubate the plate?
Paul said: "Another possibility is that YFB creates waste products which don't diffuse far from the colony and thus prevent the colony from growing very large." I'll buy that over nutrient depletion or agar drying out, at least as long as YFB isn't a swarmer.
As for the corallary, I'd think that if you streaked away radially from the edge, you should get growth again. These cells would have been the most actively growing before the growth inhibition due to the buildup of waste products, so they should resume growth right away. Besides, they taught us to inoculate from the edge of the colony, so that must be the right answer. :)
Posted by: Owen | June 24, 2010 at 08:41 PM