FIG. 4.

Plasmid content of the genomic library through nine rounds of enrichment. Plasmids were prepared from the entire library after each round of enrichment (rounds 1 to 9), fractionated by agarose gel electrophoresis, and stained with ethidium bromide. Linear DNA markers (M) were run in the first lane, and their sizes in kilobases are shown on the left side. The migration of monomeric pBluescript without inserts is indicated on the right side (pBS). Because the plasmids were not digested with restriction enzymes, covalently closed, nicked, and concatameric forms were present in the population.