INTEGRATION OF NARROW-HOST-RANGE VECTORS FROM ESCHERICHIA-COLI INTO THE GENOMES OF AMINO ACID-PRODUCING CORYNEBACTERIA AFTER INTERGENERIC CONJUGATION

Conjugative transfer of mobilizable derivatives of the Escherichia col i narrow-host-range plasmids pBR322, pBR325, pACYC177, and pACYC184 fr om E. coli to species of the gram-positive genera Corynebacterium and Brevibacterium resulted in the integration of the plasmids into the ge nomes of the recipient bacteria, Transconjugants appeared at low frequ encies and reproducibly with a delay of 2 to 3 days compared with mati ngs with replicative vectors. Southern analysis of corynebacterial tra nsconjugants and nucleotide sequences from insertion sites revealed th at integration occurs at different locations and that different parts of the vector are involved in the process, Integration is not dependen t on indigenous insertion sequence elements but results from recombina tion between very short homologous DNA segments (8 to 12 bp) present i n the vector and in the host DNA. In the majority of the cases (90%), integration led to cointegrate formation, and in some cases, deletions or rearrangements occurred during the recombination event, Insertions were found to be quite stable even in the absence of selective pressu re.