INVαF´ E. coli allow stable replication of high-copy number plasmids. The genotype of INVαF´ offers the following features:

• Blue/white screening of recombinant clones (lacZΔM15)

• Reduction of homologous recombination of transformed plasmids (recA)

• Increased quality of plasmid DNA preparations (endA1)

• Production and rescue of single-strand DNA from vectors carrying the f1 origin of replication (F´)