Biomedical subjects
Publications and source records attributed to B Diderichsen.
cur-1, a mutation found in many strains of the Y10 line of Escherichia coli K-12, but not previously described, maps at 27 min, close to galU. cur-1 causes mucoidity or uracil requirement at 29 degree C depending on the genetic background. These phenotypes are suppressed by amber codon suppressors.
Three independent relB mutants were studied. During amino acid starvation they all accumulate RNA and produce an inhibitor of in vitro protein synthesis; after starvation growth is retarded for hours. The mutants differ in the degree to which the common phenotype is expressed, but the characteristic thermolability of the inhibitor is the same. The phenotype of the relB mutants is accentuated by amber suppressors, and this effect is counteracted by a mutation, pus-1 that maps at 19.5 min near aroA.
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flu, a gene of Escherichia coli K-12, was discovered and mapped between his and shiA. It is shown that flu is a metastable gene that changes frequently between the flu+ and flu states. flu+ variants give stable homogeneous suspensions, are piliated, and form glossy colonies. flu variants aggregate, fluff and sediment from suspensions, are nonpiliated, and form frizzy colonies. flu+ and flu variants can be isolated from most strains. Implications of these observations are discussed, and it is demonstrated that flu+ variants of strain P678-54 yield three times more minicells than flu variants.
A mutant of Escherichia coli with a delayed relaxed phenotype very similar to that of a previously described relB mutant has been obtained using a new selection procedure. The mutation giving rise to this phenotype has been shown to map at 34.5 min and to be 12% cotransducible with man. It is recessive, revertible, and most likely an allele of the relB gene.
In the industrial process of liquefying starch to make glucose or high fructose syrups, it is crucial that the amylase used is stable and active at about 105 degrees C at pH 6.5 or preferentially at a lower pH. The amylase from Bacillus licheniformis is well suited for this purpose but it is possible that other amylases might perform even better. Therefore, we cloned and characterized amyS encoding a heat-stable alpha-amylase from Bacillus stearothermophilus. Using a newly developed method for creating exact gene fusions by in vivo recombination, we attempted to increase expression of amyS in Bacillus subtilis. However, only by introducing the amyS gene into B. licheniformis, we obtained significantly better yields.