Publications

plasmid incompatibility and control of replication: copy mutants of the r-factor r1 in escherichia coli k-12.	plasmid incompatibility was studied in escherichia coli k-12. by double-antibiotic selection, clones were constructed that carried the two r-factors r1 and r100, both belonging to the compatibility group fii. after release of the selection pressure, each of the two plasmids was lost at the same rate (8% per generation). mutants of r-factor r1 showing an increased number of copies per chromosome (copy mutants) were tested for their incompatibility towards r-factor r100. the results indicate that ...	1975	1102525
plasmid-mediated resistance to the bactericidal effects of normal rabbit serum.	an escherichia coli k-12 strain bearing the plasmids r1 or r100 was more resistant to the bactericidal activity of normal rabbit serum than was the same strain without a plasmid. when the plasmid r100 was transferred to several k-12 strains, the strains acquired resistance to serum bactericidal activity.	1976	786896
direction of deoxyribonucleic acid transfer and replication in a derivative of plasmid r100-1.	the site of integration and the molecular orientation of a prophage mu integrated within the resistance transfer factor component of plasmid r100-1 have been determined on the physical map of the plasmid. this allowed us (i) to determine the direction of deoxyribonucleic acid transfer from orit during conjugation and (ii) to demonstrate the unidirectionality of replication in conditions of exponential growth (by determining the strand preference of mu-specific okazaki fragments).	1979	391800
deletions in the r-determinant mer region of plasmid r100-1 selected for loss of mercury hypersensitivy.	a mutant of plasmid r100-1, which conferred cellular hypersensitivity to hg2+ because of the insertion of tn801 (tna) into the gene determining synthesis of mercuric reductase enzyme, allowed further mutational events to be selected which resulted in either reversion to hg2+ resistance (characteristic plasmid r100-1) or sensitivity at a level characteristic of plasmidless strains. restriction endonuclease ecori and bamhi analysis showed that reversion to resistance resulted from loss of tna from ...	1979	387727
transposon a-generated mutations in the mercuric resistance genes of plasmid r100-1.	a series of 23 transposon 801(tn801)-induced mutations of plasmid r100-1 from mercuric salts resistance to sensitivity was studied. although tn801 transposed frequently into the mer region of the plasmid, fine structural analysis showed that the site of insertion within mer varied. about one-half of the tn801 insertion events also caused a deletion of greater than 1 megadalton. genetic and restriction endonuclease ecori and bamhi analysis of the mutant plasmid deoxyribonucleic acid elucidated th ...	1979	387721
tn10 mediated integration of the plasmid r100.1 into the bacterial chromosome: inverse transposition.	upon integration into the bacterial chromosome the drug resistance plasmid r100.1 often loses its tetracycline resistance character. we have analyzed an hfr strain formed by such an integration and an r-prime plasmid derived from it. we find that integration took place within the tn10 transposon, that the two is10 sequences were retained, but that at least 80% of the transposon segment located between them, and carrying the tetracycline resistance genes, had been lost. we suggest that integratio ...	1979	381840
the contruction and replication properties of hybrid plasmids composed of the r-determinant of r100.1 and the plasmids pcri and psc201.	we have cloned the entire r-determinant of the antibiotic resistance plasmid r100.1 on the plasmic vectors pcr1 and psc201. we find that the hybrid plasmids segregate from cultures in which replication of the vector is blocked. this suggests that the r-det is not capable of autonomous replication.	1979	374994
properties of lambda transducing bacteriophages carrying r100 plasmid dna: mercury resistance genes.	three lambdamer (resistance to hg2+ and mercurials) transducing phages were prepared from three independent cointegrate isolates of bacteriophage lambda and plasmid r100. dna heteroduplex and restriction nuclease analyses of the lambdamer dna showed that all three phages had resulted from lambda insertion at kilobase coordinate 8.6 of plasmid r100, followed by loss of different lengths of lambda dna and replacement with different lengths of r100 dna. two of the lambdamer phages were defective, c ...	1978	363687
effects of antibiotic resistance plasmids on the bactericidal activity of normal rabbit serum.	the ability of normal rabbit serum to kill escherichia coli j6-2 was measured. with the concentration of serum adjusted so that approximately 2% of the cells survived after 2 h of incubation, there was no killing of the same strain bearing the f-like plasmid r100. other f-like plasmids also provided the host strain with resistance to serum bactericidal activity, whereas none of the i-like plasmids used provided the host strain with resistance. when e. coli j6-2 bore both r100 and an i-like plasm ...	1978	346487
involvement of is1 in the dissociation of the r-determinant and rtf components of the plasmid r100.1.	the formation of the r-determinant plc1 and of the rtf par132 from the composite plasmid r100.1 was investigated. the general location of is1 sequences on the three plasmids was established by hybridization of lambdar14 cii::is1 dna to ecori generated fragments of the various plasmids separated by agarose gel electrophoresis and transferred directly to nitrocellulose filters. the position of is1 sequences on these fragments and the homologies between fragments were analyzed by electron microscop ...	1977	331072
origin and direction of replication of the drug resistance plasmid r100.1 and of a resistance transfer factor derivative in synchronized cultures.	the origin and direction of replication of the resistance plasmid r100.1 and its resistance transfer factor derivative, par132, were studied by electron microscopy autoradiography of partially denatured molecules and partial denaturation mapping of replicative intermediates. results of these studies indicate the existence of an origin of replication at 8.8 kilobases on the r100 map. replication from this origin in cultures synchronized for initiation of replication is predominantly unidirectiona ...	1977	330504
suppression of an escherichia coli dnaa mutation by the integrated r factor r100.1: origin of chromosome replication during exponential growth.	we have investigated the behavior, during exponential growth, of strains of escherichia coli carrying a dnaa(ts) mutation that has been suppressed by the integration of the f-like r plasmid r100.1. we present evidence showing that replication in these strains proceeds largely from the normal chromosome origin at 30 degrees c, a permissive temperature for the dnaa(ts) gene product, whereas, at 42 degrees c, replication proceeds largely from the integrated plasmid. these conclusions are based on m ...	1977	328481
suppression of an escherichia coli dnaa mutation by the integrated r factor r100.1: generation of small plasmids after integration.	we have observed that integration of the r plasmid r100.1 into the chromosome of escherichia coli is associated with the formation of small, covalently closed circular elements. contour length measurements, partial denaturation mapping, and analysis of the deoxyribonucleic acid fragments produced by digestion of one of these, plc1, with the restriction endonuclease ecori indicate that it is the r-determinant element of r100.1.	1977	323231
identification of a membrane protein associated with expression of the surface exclusion region of the f transfer operon.	membrane preparations from radioactively labeled male and female strains of escherichia coli k-12 were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. an intensely labeled band corresponding to a protein of molecular weight of 24,000 was readily apparent in preparations from hfr and f-prime strains but not in those from female strains. when preparations from a series of hfr strains containing transfer operon deletions were examined, presence of the band ...	1977	321436