Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Bacteria Growth and Phases
Name: Laura
Status: Student
Grade:  9-12
Location: OR
Country: United States
Date: April 2005

Could you explain why the cells on the edges of the colony would be in the log phase of the growth curve while the cells in the center of the pile would be in either the stationary or death phases.

My guess would be that there is a higher concentration of nutrients in the medium at the edge of the colony because there are fewer cells per square cm in that area.

Ron Baker, Ph.D.

Remember that bacteria divide by binary fission, ie. the parent cell splits in half. So let's say there is one organism in the center of a plate. It divides into two and they divide into two, etc. As more cells are made, they spread out. So the cells in the center of the plate are "older" than those that have just divided on the edge. So, yes, there can be cells in different stages on the plate (or liquid culture).


Click here to return to the Molecular Biology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory