How is the p+ bacteria culture treated differently from the p- bacteria culture? (a culture is an isolated population of cells.) what is the purpose of the p- bacteria culture?

The P+ culture contains inserted DNA plasmid while P- culture does not contain DNA plasmid.The purpose of P- bacteria culture is to take it as plasmid control.

Explanation:

There are two groups of bacteria using in the lab; one is control group and second is treatment group. Control group is denoted as P- group while treatment group is denoted as P+ group. To differentiate between these two group we used the culture medium called Luria Broth with addition of an antibiotic ampicillin and the sugar arabinose.  The control group (P-) does not have plasmid stay same throughout the process because of absent of sugar arabinose. The treatment group (P+) having plasmid show more growth due to arabinose.