Genetic transformation in Streptococcus pneumoniae: molecular cloning and characterization of recP, a gene required for genetic recombination.

A 225-base-pair fragment of a recombination gene was identified by insertion-duplication mutagenesis and used as a radioactive probe to clone the corresponding rec locus from Streptococcus pneumoniae in Escherichia coli plasmid vectors. Attempts to clone large pieces of this locus were unsuccessful, but small pieces of DNA from this region were cloned in the E. coli transcriptional terminator vectors pKK232-8 and pJDC9. The extent of the rec region, 2.1 to 2.2 kilobases, was defined by determining the competence phenotype of insertion mutations constructed in vitro. A deletion of the rec locus showed it to be necessary for chromosomal integration but not for plasmid establishment. A plasmid carrying the entire locus encoded a 72-kilodalton polypeptide in a cell-free E. coli transcription-translation system.