tetracycline and Chromosome-Inversion

pBF4 is a 42-kb R plasmid from Bacteroides fragilis which transfers clindamycin resistance (Clr) independently of the chromosomal tetracycline resistance (Tcr) transfer element. We have found that this plasmid exists in two nonequimolar conformations, A and B. These forms differ by an inversion of approximately 11.5 kb which does not involve the repeated DNA sequences previously mapped on the plasmid. The presence of chromosomal tetracycline resistance conjugal elements influences the relative amounts of the two conformations: induction with tetracycline shifts the dominant form from B to A.

Topics: Bacteroides fragilis; Chromosome Inversion; Clindamycin; Conjugation, Genetic; DNA Transposable Elements; Drug Resistance, Microbial; Gene Expression Regulation, Bacterial; Nucleic Acid Conformation; R Factors; Restriction Mapping; Tetracycline; Tetracycline Resistance

We have investigated by Southern blot hybridization the rate of IS10 transposition and other Tn10/IS10-promoted rearrangements in Escherichia coli and Salmonella strains bearing single chromosomal insertions of Tn10 or a related Tn10 derivative. We present evidence for three primary conclusions. First, the rate of IS10 transposition is approximately 10(-4) per cell per bacterial generation when overnight cultures are grown and plated on minimal media and is at least ten times more frequent than any other Tn10/IS10-promoted DNA alteration. Second, all of the chromosomal rearrangements observed can be accounted for by two previously characterized Tn10-promoted rearrangements: deletion/inversions and deletions. Together these rearrangements occur at about 10% the rate of IS10 transposition. Third, the data suggest that intramolecular Tn10-promoted rearrangements preferentially use nearby target sites, while the target sites for IS10 transposition events are scattered randomly around the chromosome.

Topics: Chromosome Deletion; Chromosome Inversion; Culture Media; DNA Transposable Elements; Drug Resistance, Microbial; Escherichia coli; Galactose; Histidine; Recombination, Genetic; Salmonella; Selection, Genetic; Tetracycline

The 4150-bp plasmid pBR329 was constructed by the the insertion into pBR327 of an 877-bp DNA fragment carrying the Cmr gene from pBR328. This new cloning vector does not contain the 482-bp inverted duplication that has been reported to be present in pBR325 and pBR328 (Prentki et al., 1981). In pBR329 the Cmr gene lacks its original promoter but is transcribed counterclockwise toward the Apr gene by a promoter located to the right of the HindIII site in the Tcr gene.

Topics: Base Sequence; Chromosome Inversion; Chromosome Mapping; DNA, Bacterial; Escherichia coli; Genetic Vectors; Plasmids; R Factors; Recombination, Genetic; Repetitive Sequences, Nucleic Acid; Spectinomycin; Tetracycline

Topics: Chromosome Inversion; DNA, Bacterial; Escherichia coli; Molecular Weight; R Factors; Repetitive Sequences, Nucleic Acid; RNA, Bacterial; Tetracycline

Topics: Base Sequence; Chromosome Deletion; Chromosome Inversion; DNA Transposable Elements; Escherichia coli; Genetic Complementation Test; Mutation; Recombination, Genetic; Salmonella; Tetracycline

A simple technique has been devised that allows direct plate selection of tetracycline-sensitive clones from a predominantly tetracycline-resistant population. The technique is especially useful in genetic methodologies based on the use of tetracycline resistance transposons, such as Tn10. Potential uses of the method include selection of deletion mutants, fine-structure mapping, generalized mapping, construction of multiply marked strains, elimination of tetracycline resistance transposons and plasmids and cloning. The technique is based on our finding that tetracycline-resistant cells are hypersensitive to lipophilic chelating agents, such as fusaric acid. This finding supports the contention that certain metal ions critically facilitate tetracycline uptake and leads us to suggest possible molecular mechanisms for tetracycline resistance.

Topics: Carboxylic Acids; Cations; Chelating Agents; Chromosome Deletion; Chromosome Inversion; DNA Transposable Elements; Drug Resistance, Microbial; Fusaric Acid; Picolinic Acids; Quinolines; Salmonella typhimurium; Selection, Genetic; Tetracycline

Insertions of Tn10 are characterized by the presence of a direct repetition of a 9-bp target gene sequence on either side the insertion. The occurrence of these repetitions undoubtedly reflects an important feature of the way in which DNA molecules are broken and joined during translocation. Our experiments further suggest, however, that these 9-bp sequences are probably not responsible for Tn10-insertion specificity and that their presence is not required for normal Tn10 translocation elsewhere. We therefore suggest that the genetic information which controls the quality and quantity of Tn10 translocation actually resides somewhere other than these 9-bp sequences. We presume that much of this information lies within the ends of Tn10 itself and that signals on the target DNA which guide Tn10 to preferred positions must occur near, but not actually at, the eventual physical site of the integration event. Consideration of Tn10-promoted deletions and inversions reemphasizes the role of these ends in Tn10-promoted recombination events. Since Tn10-promoted events almost always consist in joining the physical end of one of the putative IS sequences of Tn10 to some other DNA segment, one comes again to the conclusion that these ends must contain important genetic information governing recombination events.

Topics: Bacteriophage lambda; Base Sequence; Chromosome Deletion; Chromosome Inversion; DNA Transposable Elements; DNA, Bacterial; DNA, Viral; Drug Resistance, Microbial; Recombination, Genetic; Tetracycline; Translocation, Genetic

Spontaneous tetracycline-sensitive, transfer-deficient mutants of R100-1 were selected and analysed by genetic complementation tests and with the restriction endonuclease EcoR1. While some of the Tets Tra- mutants were caused by a single deletion event which removed the Tetr genes and extended into the neighbouring transfer genes, other mutants were the result of the deletion of the Tetr genes within Tn10 which was accompanied by an inversion of adjacent DNA sequences. A clustering of deletion and inversion endpoints occurred in the traA gene. Some of the transfer genes of R100-1 were assigned to EcoR1 fragments.

Topics: Chromosome Deletion; Chromosome Inversion; Conjugation, Genetic; DNA Restriction Enzymes; DNA Transposable Elements; Escherichia coli; Genes; Genetic Complementation Test; Mutation; R Factors; Tetracycline

Topics: Chromosome Aberrations; Chromosome Deletion; Chromosome Inversion; Chromosomes, Bacterial; Drug Resistance, Microbial; Histidine; Operon; Recombination, Genetic; Salmonella typhimurium; Tetracycline

We report here the physical structures of deletions and inversions promoted by the translocatable tetracycline-resistance element Tn10. DNA/DNA heteroduplex and restriction enzyme analyses of alterations in the genome of bacteriophage lambda suggest that both types of DNA alterations almost always originate at the internal termini of the 1400 bp terminal inverted repetitions of Tn10. Tn10-promoted deletions remove a single contiguous DNA segment beginning at one such terminus; Tn10-promoted inversions are more complex, and involve both an inversion and a specific deletion of Tn10 DNA.

Topics: Chromosome Deletion; Chromosome Inversion; Coliphages; DNA, Viral; Nucleic Acid Hybridization; R Factors; Recombination, Genetic; Tetracycline; Translocation, Genetic