We know that E.coli divides in LB medium at 37C around 20-30min per cycle. In this 20-30 minutes, the bacterium has to duplicate its DNA, 4.5 million base pairs, produce every protein of its body another copy, assemble them into structures, and divide into two almost identical copies of individual bacterium.
On top of this, if we introduce a plasmid of 3kb long, 500 copies of it, into every E.coli individual, we would add some pressure to this replicating process. In this plasmid, a RFP protein expression cassette (part number J022150?) is inserted. The promoter has a lacI operon but in DH5alpha strain, its basal expression seems not under tight LacI control, probably due to weak expression levels of LacI in DH5alpha, and its huge copy numbers.
