Biomedical subjects

H Schmieger

Publications and source records attributed to H Schmieger.

50 records · Page 3Linked to original sources

PubMed1979

Bacterial DNA synthesized under phage control in a DNA-defective Salmonella-mutant and packaged into a special fraction of transducing particles of phage P22.

Lysates of P22 contain a small fraction of transducing particles with bacterial DNA replicated semiconservatively after the time of infection. It was demonstrated that the presence and relative amount of this class of transducing particles was unchanged, if infection of Salmonella occured under a condition nonpermissive for bacterial DNA replication. Analysis of particles with DNA fragments derived from different regions of the Salmonella chromosome indicated that the replication of the bacterial DNA carried by these transducing particles was not initiated specifically at the normal origin for bacterial chromosome replication.

DNA Replication↗

PubMed1979

In vitro packaging of exogenous DNA by Salmonella phage P22.

We describe in vitro conditions for packaging of exogenous DNA of Salmonella phage P22 which has terminally redundant, circularly permuted DNA. The method is a modification of the Kaiser-Masuda procedure. The most important aspect is to prepare all components (proheads, enzymes and concatemeric DNA) in end- cells. The influence of several factors such as DNA- and Mg2+ concentration and kinetics has been investigated.

Adenosine Triphosphate↗

PubMed1979

Phage Mu mutants with increased transduction abilities.

Mutants of the Escherichia coli phage Mu with increased transduction frequencies are describe. These mutants can be subdivided as (i) mutants in which only the marker used for detection is affected and (ii) mutants in which all other markers tested are also effected, but not to the same extent. The possible mechanisms of the altered transducing properties are discussed.

Coliphages↗

PubMed1976

Altered cotransduction frequencies exhibited by HT-mutants of Salmonella-phage P22.

Phage P22-mutants with increased transduction ability (HT-mutants) show in comparison to wild type 22, different frequencies of contransduction for markers on two different transducing fragments of the Salmonella chromosome. The data are interpreted as indicating that host DNA to be packaged is cut by HT-mutants at sites different from those cut by wild-type phage, due to an altered specificity of the nuclease responsible for this step.

DNA, Bacterial↗

PubMed1975

Appearance of transducing particles and the fate of host DNA after infection of Salmonella typhimurium with P22-mutants with increased transducing ability (HT-mutants).

The kinetics of production of transducing particles for different bacterial markers were followed by premature lysis of Salmonella typhimurium cells infected with P22 phages. The were compared for cells infected with wild type phage or with HT-mutants which show increased transduction frequencies. Measuring the sedimentation velocity of bacterial DNA of cells infected with wild type or HT-phages, it was shown that: a) there is no cutting of DNA at random; b) original fragments necessary for packaging host DNA into transducing particles cannot be smaller than 10 phage-genome lengths; c) cutting of transducing fragments leads immediately to the right length; d) there is no loss of precipitable DNA due to phage infection.

DNA, Bacterial↗

PubMed1974

Phage genes involved in the formation generalized transducing particles in Salmonella--Phage P22.

Phage P22-mutants with increased or decreased ability to produce transducing particles (HT-1 and NT-mutants) were submitted to mapping experiments. The gene responsible for HT-phenotype was found to be allelic to gene 3 of the P22 linkage map. For the NT-phenotype different genes were identified: gene 1 (or a new gene extremely close to it), gene 5, gene 8 and a new gene between genes 3 and 19.

Alleles↗

PubMed1974