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Biomedical subjects

E A Birge

Publications and source records attributed to E A Birge.

14 recordsLinked to original sources
PubMed1987

Characterization of phage 18, an unstable coliphage.

Phage 18, a noninducible coliphage, is quite unstable and therefore difficult to study. Newly developed very gentle lysis and mounting techniques yielded isolated virions for examination by electron microscopy. The phage has a contractile tail with a length of 130 nm and an isometric head with a capsid diameter of 50 nm. Phage 18 is similar in morphology to phage P2 but is heteroimmune to it. DNA extracted from a clear-plaque mutant of phage 18 was subjected to BamHI restriction endonuclease digestion and was found to be easily distinguishable from the published restriction patterns for P2, phage 299, or phage 186 DNA. The genome size was calculated to be 33.5 kb. Using the DNA melting point, phage 18 DNA (G+C) content was determined to be 55.0% and its buoyant density was determined to be 1.715.

Coliphages↗
PubMed1985

Isocitrate dehydrogenase assays on intact bacterial cells.

A qualitative assay which can be adapted to screen large numbers of Escherichia coli colonies for the presence of soluble enzymes is described. In a test of the system using a new, especially sensitive assay for isocitrate dehydrogenase activity, colonies producing the enzyme could be correctly identified at the 70% level after 2 h of incubation and at the 100% level after 8 h of incubation. The completed reactions are stable for several days at room temperature.

Chemical Phenomena↗
PubMed1983

Site-specific recombination following conjugation in Escherichia coli K-12.

In accord with the observations of other workers, unselected marker analysis of Escherichia coli K-12 transconjugants isolated from matings involving several different Hfr strains as donors has shown that most genetic exchanges are clustered either near the selected marker or near the origin of the transferred Hfr DNA. The present work increases the number of Hfr strains tested and shows that the clustering of the recombinational events near the origin of transfer is statistically significant. It is proposed that this clustering of genetic exchanges is due to the action of a unique recombination system (site-specific conjugal recombination or ssr) which recognizes the early transferred portion of the F plasmid and catalyzes a genetic exchange in or near the adjacent bacterial DNA. Twelve Hfr strains representing eleven different points of origin were tested, and only KL16 and Ra-1 did not demonstrate the typical clustering of genetic exchanges. Since these strains share a common transfer origin, they may represent spontaneous mutations affecting the ssr system.

Conjugation, Genetic↗
PubMed1974

Isolation and characterization of an Escherichia coli K-12 mutant with a temperature-sensitive recA- phenotype.

A mutation that causes a temperature-sensitive RecA(-) phenotype was identified in a derivative of a PolA(-) strain that failed to grow at high temperature. The mutant allele (recA200) was shown to be linked to cysC, conferred a sharply temperature-sensitive, ultraviolet-sensitive Rec(-) phenotype in the range 35 to 42 C, and in crosses failed to show complementation at 42 C with Hfr's that transferred recA(-). Double mutants that carried both recA200 and polA were examined for ability to grow and synthesize DNA at restrictive temperatures.

Alleles↗
PubMed1969

Altered ribosomal protein in streptomycin-dependent Escherichia coli.

We have compared the 30S ribosomal proteins of strains of Escherichia coli sensitive to and dependent on streptomycin and identified a single protein that is functionally altered in the ribosomes dependent on streptomycin. This protein (30S-15) is the same protein that is functionally altered in ribosomes resistant to streptomycin.

Bacterial Proteins↗
PubMed1969

Structural determinant of a ribosomal protein: K locus.

One of the ribosomal proteins (30S-8B) of Escherichia coli B has a greater electrophoretic mobility than the homologous protein (30S-8K) in E. coli K. The amino acid compositions, tryptic peptides, and cyanogen bromide peptides of these two homologous proteins unambiguously indicate that the genetic locus which determines the electrophoretic mobility of protein 30S-8 is the structural gene for this protein.

Amino Acid Sequence↗