Isolation of Bacterial Colonies
The isolation of a single colony is important in almost every experiment. The generation time of E.coli is short. During this time many mutations in the DNA may have occurred. To solve for this problem it is recommended to only use one colony in the experiment. To isolate a colony you take a loop and inoculate it. Then you pick up a section of bacteria from the starting plate. This is then streaked onto a new plate in a single line in one direction (not back and forth). The loop is then reinoculated, and the plate is turned 90˚. The single streak is then spread along another single line 90˚ from the first streak. The loop is inoculated again and the plate is turned another 90˚ . The second streak is then used to make the next line. This is done one last time. The bacteria on the plate should look like a box. When the colonies grow, the colonies on the last streak should be far enough apart that individual colonies can be taken off.