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Biomedical subjects

R S Hanson

Publications and source records attributed to R S Hanson.

62 records · Page 4Linked to original sources
PubMed1969

Relationship between glucose utilization and growth rate in Bacillus subtilis.

The effect of growth rate on the rate of glucose utilization has been examined with a sporogenic and a weakly sporogenic strain of Bacillus subtilis by means of the continuous culture technique. Cultures were grown aerobically on a mineral salts medium with glucose as the carbon and energy source. During both nitrogen and l-tryptophan limitation, the rate of glucose consumption (milligrams of glucose per hour per milligrams of cells) decreased when the growth rate was decreased. The coupling between the rate of glucose disappearance and the growth rate was estimated as 76 to 86% during nitrogen limitation and as 60 to 78% during tryptophan limitation. Sporulation had no detectable influence on the coupling.

Bacillus subtilis↗
PubMed1968

Microcycle sporogenesis of Bacillus cereus in a chemically defined medium.

A chemically defined medium which allowed germination, outgrowth, and subsequent resporulation of Bacillus cereus T spores, without intervening cell division (microcycle sporogenesis), is described. No medium replacement was required. The second-stage spores were heat-stable and had similar germination characteristics and dipicolinic acid content to primary spores. Deoxyribonucleic acid (DNA) replication began soon after germination and there was a doubling in the DNA content of the cells within 2 hr.

Bacillus cereus↗
PubMed1967

Effect of different nutritional conditions on the synthesis of tricarboxylic acid cycle enzymes.

The effect of various nutritional conditions on the levels of Krebs cycle enzymes in Bacillus subtilis, B. licheniformis, and Escherichia coli was determined. The addition of glutamate, alpha-ketoglutarate, or compounds capable of being catabolized to glutamate, to a minimal glucose medium resulted in complete repression of aconitase in B. subtilis and B. licheniformis. The synthesis of fumarase, succinic dehydrogenase, malic dehydrogenase, and isocitric dehydrogenase was not repressed by these compounds. It is postulated that glutamate or alpha-ketoglutarate is the true corepressor for the repression of aconitase. A rapidly catabolizable carbon source and alpha-ketoglutarate or glutamate must be simultaneously present for complete repression of the formation of aconitase. Conditions which repress the synthesis of aconitase in B. subtilis restrict the flow of carbon in the sequence of reactions leading to alpha-ketoglutarate but do not prevent glutamate oxidation in vivo. The data indicate that separate and independent mechanisms regulate the activity of the anabolic and catabolic reactions of the Krebs cycle in B. subtilis and B. licheniformis. The addition of glutamate to the minimal glucose medium results in the repression of aconitase, isocitric dehydrogenase, and fumarase, but not malic dehydrogenase in E. coli K-38.

Bacillus↗
PubMedDate not supplied

Genetics of methane and methanol oxidation in gram-negative methylotrophic bacteria.

Within the past few years, considerable progress has been made in the understanding of the molecular genetics of methane and methanol oxidation. In order to summarize this progress and to illustrate the important genetic methods employed, this review will focus on several well-studied organisms. These organisms include the gram-negative faculative methylotrophs Methylobacterium extorquens, Methylobacterium organophilum and Paracoccus denitrificans. In addition, the obligate methanotrophs Methylococcus capsulatus and Methylosinus trichosporium are discussed. We have chosen not to discuss the genetics of methanol oxidation in the yeasts or in gram-positive bacteria. Likewise, the genetics of related topics (for example, methylamine oxidation and carbon assimilation pathways) are not reviewed here. Broad host range conjugatable plasmids have enabled researchers to complement mutations and clone genes from gram-negative methylotrophic bacteria. More recently, 'promoter probe' derivative plasmids have been used to elucidate aspects of gene regulation. Also, alternative gene-cloning techniques are proving useful in circumventing problems in the genetic studies of the obligate methanotrophs, the group of bacteria that is the most refractory to traditional methods.

Cloning, Molecular↗