Characterization of translucent segments observed in an smbA mutant of Escherichia coli

Abstract The smbA gene of Escherichia coli is essential for cell proliferation. The smbA2 mutant shows cold-sensitive colony formation at 22°C. A novel morphological phenotype, formation of a translucent segment at midcell or at a cell pole, was observed by phase-contrastt microscopy at a high frequency in the smbA2 mutant cells incubated in L medium lacking NaCl at 22°C, but not observed in L medium containing 1% NaCl or 20% sucrose at the same temperature. No translucent segment was observed in the wild-type cells in any of the media used. Electron microscopic observation revealed that the translucent segments resulted from the enlargement of a periplasmic space by separation of the inner membrane from the peptidoglycan layer and the outer membrane.     

Isolation and Characterization of a Filamentous Phage,Vf33, Specific for Vibrio parahaemolyticus

Phage Vf33, a filamentous phage about 1,400 nm long and 7 nm wide, specific for Vibrio parahaemolyticus, was isolated and characterized. The buoyant density of Vf33 in CsCl was 1.292 g/cm³. As with other filamentous phages, the lytic activity of Vf33 was resistant to heating below 80 C and to treatment with diethylether, acetone or methanol but sensitive to chloroform. The nucleic acid of this phage is single-stranded circular DNA 8.4 kb in size. The viral genome was converted to a double-stranded replicative form in the host cell. Among the strains tested, only V. parahaemolyticus strains possessing K38 antigen was sensitive to the phage.     

Intervention of somatic mutational events in vivo by a germline defect at the adenine phosphoribosyltransferase locus

Both germline and somatic mutations are known to affect phenotypes of human cells in vivo. In previous studies, we cloned mutant peripheral blood T cells from germline heterozygous humans for adenine phosphoribosyltransferase (APRT) (EC 2.4.2.7) deficiency and found that approximately 1.3 × 10^–4 peripheral T cells had undergone in vivo somatic mutations. Loss of heterozygosity (LOH) was the major cause of the mutations at the APRT locus since approximately 80% of the mutant T cell clones exhibited loss of normal alleles. In the present study, we identified three heterozygous individuals for APRT deficiency (representing two separate families), in whom none of the somatic mutant cells exhibited LOH at the APRT locus. The germline mutant APRT alleles of these heterozygotes from two unrelated families had the same gross DNA abnormalities detectable by Southern blotting. None of the germline mutant APRT alleles so far reported had such gross DNA abnormalities. The data suggest that the germline mutation unique to these heterozygous individuals is associated with the abrogation of LOH in somatic cells. The absence of LOH at a different locus has already been reported in vitro in an established cell line but the present study describes the first such event in vivo in human individuals. Received: 10 May 1996     

Isolation of a cDNA clone encoding mouse 3-hydroxyacyl CoA dehydrogenase

Rae-38, a cDNA clone isolated from mouse embryonal carcinoma F9 cells, was sequenced, and the deduced RAE-38 protein showed about 86% homology to pig 3-hydroxyacyl CoA dehydrogenase (HCDH; EC 1.1.1.35). This clone can be used to elucidate the regulatory mechanism of HCDH gene expression in mammals.     

Condensation of oligoglycines with trimeta- and tetrametaphosphate in aqueous solutions

The dehydration condensation of glycine with trimetaphosphate in aqueous solution has been reinvestigated. Although it has been reported that the condensation of glycine under the alkaline conditions was brought about through the formation of cyclic acylphosphoramidate and hence the condensation of polyglycines could not occur, we found that the condensation of oligoglycines with trimeta- and tetrametaphosphate in aqueous solution are possible through the formation of their acylphosphates under the neutral or weak acidic conditions.Aqueous solutions of 1.0 M glycylglycine and 1.0 M trimetaphosphate in the various pH from 4.0 to 9.0 were incubated at 38 °C. The solutions were analyzed by HPLC with ninhydrin reaction system. Tetraglycine and hexaglycine were detected and their maximum yields were given in the reaction carried out around pH 7. They are approximately 15% and 4% after 30 days, respectively. Analogous experiments were performed with tetrametaphosphate. The results showed a similar pH dependence for the condensation, but the yields were about one-tenth of those of corresponding experiments with trimetaphosphate.Relative rates of dimerization of glycine, diglycine and triglycine in the equimolar concentration were also investigated at pH 6.0 at 38 °C. The rates for digylcine and triglycine were approximately twice and four times as large as that for glycine.Relevance of the experiments to chemical evolution is discussed.