Biomedical subjects

W P Hoekstra

Publications and source records attributed to W P Hoekstra.

6 recordsLinked to original sources

PubMed1979

On the role of the recipient cell during conjugation in Escherichia coli.

To study the role of the E. coli recipient cell in conjugation recipient cell mutants deficient in conjugation (Con-) were isolated. Mutants specific for F-type E. coli donor cells (ConF-) and mutants specific deficient in conjugation with I-type donor cells (ConI-) were isolated. Both ConF- and ConI- mutants were blocked in stable mating pair formation. Biochemical analysis of the mutants suggests that the outer membrane protein coded by the ompA gene and LPS are important for recipient activity in F-type conjugation while LPS is important for recipient activity in I-type conjugation.

Bacterial Proteins↗

PubMed1977

Characterization of the E. coli K12 strain AB1157 as impaired in guanine/xanthine metabolism.

The widely used E. coli K12 strain AB1157 is impaired in guanine (xnathine) metabolism. Mutants blocked in purine biosynthesis before the stage of inosine monophosphate synthesis do not grow on external guanine or xanthine. The genetic nature of the Gua/Xan lesion is a deletion in the chromosome that covers the proA gene. The lesion causes reduced uptake of guanine.

Chromosome Mapping↗

PubMed1976

Conjugation deficient E. coli K12 F- mutants with heptose-less lipopolysaccharide.

Two F- mutants deficient in conjugation with F-type donors are isolated and characterized. Phenotypically, these mutants are similar; they have heptose-less lipopolysaccharide and lack some outer membrane protein. Genotypically, they are different. One mutant harbors a point mutation in the 70 to 74 min region, while the other is deleted for the chromosomal region 6.5 to 8.5 min. Comparison of the properties of the conjugation-deficient mutants described in this paper with other such mutants suggests that an outer membrane protein is the receptor for the f-pilus.

Binding Sites↗

PubMed1976

Transformation in E. coli K12: relation of linkage to distance between markers.

E. coli K12 transformants, selected as leu+ or pyrA+ transformants, were analysed for inheritance of some closely linked unselected markers. Based on the observation that the number of recombinants which require, besides an integration event, one or more crossing-over events was negligible, a simple mapping function was deduced. The function L= e-kd, which directly relates observed linkage of an unselected marker and the relative distance of that unselected marker to the selected marker, gave a consistent interpretation of the experimental results.

Chromosome Mapping↗

PubMed1976

Characterization of an Escherichia coli K-12 F-Con-mutant.

An Escherichia coli K-12 F-mutant defective in conjugation was isolated by means of a zygotic induction enrichment procedure. The recipient ability of the mutant was reduced about 50 times owing to a block in one of the first steps of the conjugation process. In the mutant, cell envelope alterations could not be observed. Sensitivity toward detergents, antibiotics, and phages was unaltered. The mutation appeared to be co-transducible with pyrD. The linkage order in the region of the mutation is origin KL 99-con-pyrD-aroA.

Anti-Bacterial Agents↗

PubMed1975

Conjugation in Escherichia coli: a study of recombination and the fate of donor DNA at the level of the zygote.

We have developed an experimental system for studying concomitantly the fate of the donor DNA and the process of recombination after conjugation in Escherichia coli. We used a set of Hfr and F-strains carrying complementing lacZ mutations. Expression of the lacZ allele on the chromosomal fragment derived from the donor results in the formation of heat sensitive beta-galactosidase by complementation. By intragenic recombination between the two lacZ mutations a lacZ+ gene may be formed, and wild type beta-galactosidase will be synthesized subsequently. So the assay of heat sensitive and wild type beta-galactosidase enabled us to follow respectively the fate of the donor DNA and the recombination process. Using various recombination deficient recipient strains, we found that the donor DNA is progressively inactivated in recA, rec-34 and recH recipients, although the initial rate of expression is equivalent to that in a Rec+ recipient; no significant recombination was observed. In Rec+, recB or recG recipients there was no inactivation and recombination occurred. The kinetics of recombinant formation in the recB strain seems to differ from the wild type; in a recG recipient the recombination activity is significant, but lower than in the wild type recipient.

Conjugation, Genetic↗