Monitoring of chromosomal insertions of the IncJ elements R391 and R997 inEscherichia coli K-12

The integration site(s) of the IncJ element, R391, was localised to a speci fic region of the Escherichia coli chromosome, between the uxuA and serB lo ci (98.0-99.5 min), using classical Hfr mapping techniques. F-prime plasmid hosts, diploid for regions spanning the E. coli chromosome, were used as r ecipients in R391 and R997 conjugal transfer assays. Analysis of transconju gants revealed the integration of R391 and R997 into specific F-primes that contain the uxuA to serB region, but not F-primes that contain other regio ns of the chromosome. A comparison of the electrophoretic mobility of the o riginal F-primes with those containing inserts demonstrated the integration of large elements, in excess of 85 kb. Linear integration of the IncJ elem ents into chromosomal DNA was demonstrated in recombination-deficient (recA ) backgrounds in the absence of delectable autonomous stages. These observa tions account for the inability to isolate plasmid DNA from IncJ hosts, and suggests that the elements exhibit a conjugative transposon-like biology i n E. coli. (C) 1999 Federation of European Microbiological Societies. Publi shed by Elsevier Science B.V. All rights reserved.