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W B Dempsey

Publications and source records attributed to W B Dempsey.

At least 37 records · Page 2Linked to original sources
PubMed1979

Lambda transducing phages derived from a FinO- R100::lambda cointegrate plasmid: proteins encoded by the R100 replication/incompatibility region and the antibiotic resistance determinant.

Three lambda transducing phages have been isolated from pEDR20, an R100::lambda cointegrate plasmid in which the lambda insertion inactivated the R100 finO gene. Physical analysis of the three phages showed that the lambda is inserted at kilobase coordinate 81.3 of R100. All three phages carry different amounts of R100 DNA in the left arm of lambda. Each pahge contains ISlb, the mer genes and the region between coordinate 81.3 and 88.6; thus, all contain the genes necessary for R100 replication. One phage, VA lambda 73, contains the entire r-determination of R100 in addition to the above DNA. Five proteins coded by the region between 81.3 and 88.6 were detected. These had subunit molecular weights of 10,400; 12,200; 16,200; 19,600; and 38,300. The first was made constitutively and the other four only from a lambda promoter. Other constitutive proteins were one from the cml fus region with a molecular weight of 22,400 (cml) and two from the str sul region with molecular weights of 31,500 (str?) and 30,100 (sul?). Mercuric ion induced synthesis of at least 10 proteins. Six of these were known from earlier work. The total size of the proteins which appear to derive from the mer genes exceeds by a factor of 1.5, the coding capacity of this region without overlapping genes. Some, or all of these extra proteins may be chromosomal in origin, possibly derepressed in response to mercury gene products.

Bacteriophage lambda↗
PubMed1978

Pyridoxine-requiring mutants of Escherichia coli: glycolaldehyde dehydrogenase is not coded for by the pdxB gene.

Twenty-seven independent pyridoxineless mutants belonging to genetic linkage group I were assayed for glycolaldehyde dehydrogenase. Some mutants lacked enzyme activity entirely, and others showed activity ranging from very low to wild-type levels. Reversion to pyridoxine independence usually had no effect upon this activity. Transfer of the pyridoxine genes to a common host that had wild-type levels of enzyme activity made the recipient pyridoxineless without affecting the activity. These results negate the idea of an obligatory role for glycolaldehyde dehydrogenase in pyridoxine biosynthesis.

Acetaldehyde↗
PubMed1978

3-hydroxypyruvate substitutes for pyridoxine in serC mutants of Escherichia coli K-12.

Escherichia coli K-12 mutants with serC genotype required pyridoxine and serine for normal growth, as do E. coli B mutants of this type. Mutants of the K-12 strain, however, reverted easily to pyridoxine independence without regaining activity in the 3-phosphoserine oxoglutarate transaminase coded for by the serC gene. Both these revertants and the parental type synthesized pyridoxine in normal amounts when 3-hydroxypyruvate was used as a supplement, although neither of these mutants could use this compound to satisfy their serine requirement. Since serine alone was inadequate to provide the nutritional requirement of serC mutants, these mutants must have been unable to synthesize 3-hydroxypyruvate from serine. We suggest that 3-phosphoserine oxoglutarate transaminase in normal E. coli serves as a catalyst for transaminating small amounts of serine to 3-hydroxypyruvate, which is then used in pyridoxine biosynthesis. In serC mutants, this activity is blocked, and these mutants then show a double requirement for serine and pyridoxine.

Escherichia coli↗
PubMed1978

Properties of lambda transducing bacteriophages carrying R100 plasmid DNA: mercury resistance genes.

Three lambdamer (resistance to Hg2+ and mercurials) transducing phages were prepared from three independent cointegrate isolates of bacteriophage lambda and plasmid R100. DNA heteroduplex and restriction nuclease analyses of the lambdamer DNA showed that all three phages had resulted from lambda insertion at kilobase coordinate 8.6 of plasmid R100, followed by loss of different lengths of lambda DNA and replacement with different lengths of R100 DNA. Two of the lambdamer phages were defective, containing deletions from lambdaatt through the lambdaN gene and into the lambdarex gene; the third, VAlambda14, was an N+ Spi- plaque-forming phage. With VAlambda14, N-dependent transcription of R100 mer from the lambdapL promoter suggested that transcription of mer proceeded in the direction from IS1b toward the sulfonamide resistance determinant (i.e., from a plasmid promoter in restriction nuclease fragment EcoRI-H toward fragment EcoRI-I). Phage-directed protein synthesis in a UV-irradiated lambdaind- lysogen showed the Hg2+-inducible synthesis of three major polypeptides of molecular weights 68,000, 11,500, and 8,500 and three minor ones of molecular weights 54,000, 33,000, and 13,500. The largest of the major polypeptides is identified as the subunit of the mercuric reductase enzyme. The functions of the smaller polypeptides are not known. Hg2+ reductase enzyme assays confirmed the regulation of mer synthesis during phage infection.

Bacterial Proteins↗
PubMed1976

Plasmid co-integrates of prophage lambda and R factor R100.

Single and tandem insertions of prophage lambda into R100 have been isolated. Insertions into the transfer genes, insertions into the transfer control gene finO, and insertions into regions that result in no detectable phenotypic change were found. From the last type, deletion mutants were isolated which established the sequence of antibiotic resistance genes as tet-cml-fus-str-sul-mer in R100. High frequency transducing phage preparations lambdamer, lambdasul str, and lambdasul str cml were also isolated from this type.

Anti-Bacterial Agents↗
PubMed1975

Incorporation of pantothenate into citrate lyase by a pantothenateless mutant of Klebsiella pneumoniae.

A pantothenate-requiring mutant of Klebsiella pneumoniae was isolated. The mutant showed an absolute dependence on pantothenate for growth. When grown in the presence of [14C]pantothenate, the mutant incorporated [14C]pantothenate into citrate lyase (3.4 mol/mol of enzyme). Analysis of a double-labeled enzyme ([14C]pantothenate and [3H]acetate) by gel electrophoresis in sodium dodecyl sulfate showed that both 3H and 14C were associated solely with the smallest subunit, the acyl carrier protein of citrate lyase.

Acetates↗
PubMed1973

Glycolaldehyde is a precursor of pyridoxal phosphate in Escherichia coli B.

Carbon-labeled glycolaldehyde prepared from [(14)C]serine was used to supply the nutritional requirement of a pyridoxineless auxotroph of Escherichia coli. Pyridoxal phosphate isolated from bacteria so grown was found to have incorporated the radioactive glycolaldehyde with little dilution. The radioactivity which was unincorporated into pyridoxal phosphate was recovered almost entirely in the culture fluid. The results establish for the first time that glycolaldehyde is indeed a natural precursor of pyridoxal phosphate or it is readily converted to such a precursor.

Aldehydes↗
PubMed1973

Lysis of Escherichia coli by glycine is potentiated by pyridoxine starvation.

Pyridoxineless mutants of Escherichia coli are lysed in a few hours when starved for pyridoxine in a glucose minimal medium containing glycine at 10 mM. The lysis is prevented equally well by l-alanine and by d-alanine when either is present at 0.1 mM. The lysis is potentiated by 0.5 mM l-methionine. The peculiar susceptibility of E. coli B to glycine-mediated lysis during starvation for pyridoxine suggests that the starvation reduces the availability of some normal antagonist of glycine, presumably alanine.

Alanine↗
PubMed1972

Isoleucine and threonine can prolong protein and ribonucleic acid synthesis in pyridoxine-starved mutants of Escherichia coli B.

Pyridoxineless mutants of Escherichia coli B stopped incorporation of nucleosides into trichloroacetic acid-insoluble material about 40 to 60 min after pyridoxine starvation was initiated, whereas incorporation of amino acids (measured the same way) slowed but did not stop for several hours. Both these incorporations and cell density were increased most effectively by the presence of either threonine or isoleucine. Arginine, glutamate, histidine, methionine, tryptophan, and tyrosine also caused significant but less dramatic increases. Inducibility of beta-galactosidase continued beyond the point where nucleic acids appeared to stop their synthesis, suggesting that messenger ribonucleic acid synthesis continued beyond ribosomal ribonucleic acid synthesis. This inducibility was also increased by isoleucine and threonine. The overall results suggest that the threonine-isoleucine biosynthetic pathway is the most sensitive to starvation for pyridoxine.

Amino Acids↗
PubMed1971

Identification of the forms of vitamin B 6 present in the culture media of "vitamin B 6 control" mutants.

An Escherichia coli mutant resistant to isoniazid (WG497) contained 0.6 mumole of extracellular pyridoxamine and pyridoxamine phosphate in the early stationary phase. A suppressed lysine mutant (AT1024) contained 1.4 mumoles of pyridoxal phosphate under the same conditions. The internal concentration of vitamin B(6) was one-half of normal for AT1024 and increased fivefold for WG497.

Biological Assay↗
PubMed1971

Control of vitamin B 6 biosynthesis in Escherichia coli.

Pyridoxineless mutants of Escherichia coli B which specifically require pyridoxal or pyridoxamine for growth can be divided into classes according to their growth responses in enriched media. Members of the slowest growing class synthesize vitamin B(6) at the fastest rates when starved for pyridoxal in glycerol minimal medium. After 80 min of synthesis at 4 x 10(-10) moles of vitamin B(6) per mg of cells per hr, the rate increases four- to fivefold and continues at the new rate for several hours. The shift to the new rate is prevented by chloramphenicol, thus suggesting that a derepression mechanism exists to control vitamin B(6) synthesis in addition to the previously discovered feedback control.

Alcohol Oxidoreductases↗
PubMed1971

Role of vitamin B 6 biosynthetic rate in the study of vitamin B 6 synthesis in Escherichia coli.

Nutritional auxotrophs of Escherichia coli synthesize vitamin B(6) compounds at a rate of 1 x 10(-10) to 2 x 10(-10) moles per hr per mg (dry weight) of cells when they are suspended in minimal medium lacking their required nutrients. A few auxotrophs have been found to stop or reduce vitamin B(6) synthesis during such an experiment. These include thiamineless, citrate synthaseless, and pyridoxineless mutants as well as mutants which require four carbon compounds for growth. Glycolaldehyde was found to restore vitamin B(6) synthesis in the last named of these mutants without restoring normal growth. A class of pyridoxineless mutants which responded with normal growth to 0.4 mm glycolaldehyde or 0.15 x 10(-3) mm pyridoxol was also found. The results suggest that a thiamine pyrophosphate-requiring step as well as glycolaldehyde may be involved in pyridoxal phosphate biosynthesis.

Acetates↗