Adenine + thymine content of different genes located on the broad host range plasmid RP4

Burkardt HJ, Pühler A, Wohlleben W. Adenine + thymine content of different genes located on the broad host range plasmid RP4. J Gen Microbiol. 1980;117(1):722-722.The genetic map of plasmid RP4 was correlated with its adenine+thymine (AT) map. For this purpose, RP4 DNA was digested with one or both of the restriction enzymes EcoRI and HindIII and the resulting linear RP4 molecules and fragments were partially denatured, examined in the electron microscope and their AT maps were determined using a computer program. From these AT maps the EcoRI and HindIII restriction sites were located on the AT map of RP4. Since the positions of these restriction sites on the genetic map of RP4 are known, the maps could be compared. They revealed a high AT content for the Tn1 transposon and the kanamycin resistance gene. The tra-1 region is also distinguished by a sharply defined AT-rich region, whereas tra-2 and the tetracycline resistance gene have an AT content which is not distinctly different from the average AT content of RP4

Cloning of the entire region for nitrogen fixation from Klebsiella pneumoniae on a multicopy plasmid vehicle in Escherichia coli

Pühler A, Burkardt HJ, Klipp W. Cloning of the entire region for nitrogen fixation from Klebsiella pneumoniae on a multicopy plasmid vehicle in Escherichia coli. Mol Gen Genet. 1979;176(1):17-24

Relationship of group P1 plasmids revealed by heteroduplex experiments: RP1, RP4, R68 and RK2 are identical

Burkardt HJ, Riess G, Pühler A. Relationship of group P1 plasmids revealed by heteroduplex experiments: RP1, RP4, R68 and RK2 are identical. J Gen Microbiol. 1979;114(2):341-348.The molecular relationships of the IncP1 plasmids RP1, RP4, R68 and RK2 were tested by electron microscopic examination of heteroduplexes. In several hybridization experiments molecules were detected which had a 7.8% portion of incomplete reannealing. This 'heterologous region' could be explained by the typical renaturation behaviour of the transposon Tn1. The identity of the Tn1 transposon present in RP1 and RP4 was proved by heteroduplex experiments with lambda phage DNA containing this transposon. These results indicated that the plasmids RP1 and RP4 are identical. Additional heteroduplex experiments between plasmids R68.45 and RP8 and between R68.45 and RK2 were performed. R68.45, a derivative of R68, has a small DNA insertion and RP8 can be regarded as a large insertion mutant of RP4; both insertions were used as single-stranded hybridization markers. From the hybrid molecules formed, it was deduced that R68 and RK2 are identical with RP1 and RP4 as far as molecular structure is revealed by the technique used

ISR1 - AN INSERTION ELEMENT ISOLATED FROM THE SOIL BACTERIUM RHIZOBIUM-LUPINI

Priefer UB, Burkardt HJ, Klipp W, Pühler A. ISR1 - AN INSERTION ELEMENT ISOLATED FROM THE SOIL BACTERIUM RHIZOBIUM-LUPINI. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY. 1981;45 Pt 1:87-91

Electron microscopy and computerized evaluation of some partially denatured group P resistance plasmids

Burkardt HJ, Mattes R, Pühler A, Heumann W. Electron microscopy and computerized evaluation of some partially denatured group P resistance plasmids. J Gen Microbiol. 1978;105(1):51-62.DNA of the R plasmids RP1, RP4 and RP8 was isolated from various hosts. The lengths of these plasmid molecules were determined by electron microscopy: RP1 and RP4 were about 19 micron long, RP8 measured 31 micron. An RP4 plasmid mutant, designated RP4a, was isolated from Escherichai coli; it was about 1 micron shorter than normal RP4 DNA. To investigate the molecular relationship between RP4, RP4a and RP8 DNAs of these plasmids were partially denatured and examined in the electron microscope. Measurements of the length and denaturation pattern of the DNA molecules were used to construct physical maps. A new computer program was devised for the alignment of the circular molecules, and the effect of variations of different parameters on the reliability of the program was tested. A comparison of the denaturation pattern of RP4 and RP8 indicated that RP8 was composed of total RP4 plus an additional DNA fragment. The RP4a mutant plasmid could be defined as a deletion mutant with loss of 1 micron DNA

Morphological and molecular characterization of several actinophages isolated from soil which lyse Streptomyces cattleya or S. venezuelae

Anné J, Wohlleben W, Burkardt HJ, Springer R, Pühler A. Morphological and molecular characterization of several actinophages isolated from soil which lyse Streptomyces cattleya or S. venezuelae. Journal of General Microbiology. 1984;130(OCT):2639-2649