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Biomedical subjects

R S Hanson

Publications and source records attributed to R S Hanson.

At least 55 records · Page 3Linked to original sources
PubMed1978

Molar growth yields and enterotoxin B production of Staphylococcus aureus S-6 with amino acids as energy sources.

Staphylococcus aureus S-6 was able to utilize glutamate, proline, histidine, aspartate, alanine, threonine, serine, or glycine as a major energy source, when these were added singly at a concentration of 2.5 g/liter to a base medium containing salts, vitamins, and 30 mg of each of 18 amino acids per liter. Molar growth yields (Y) for each of the eight amino acids were determined in aerobic batch cultures. Except with aspartate and serine, all molar growth yields decreased with increasing concentration of the energy source, whether or not it was present in excess. The average molar growth yields for both aspartate and serine were Y = 35 g/mol. The highest Y values obtained with the other amino acids were 79, 78, 56, 46, 58, and 21 g/mol for glutamate, proline, histidine, alanine, threonine, and glycine, respectively. Histidine was not utilized as an energy source at concentrations of less than 2 mM. Enterotoxin yields (mg of toxin per g [dry wt] of cells) higher than in the basal medium were obtained when proline, histidine, alanine, serine, and glycine were the major energy sources. When proline and alanine were the major energy sources, enterotoxin yields were not affected by the concentration, whereas toxin yields were reduced at high concentrations of the other six amino acids. The highest cell yields and Y values were obtained with glutamate, but its utilization as an energy source markedly reduced enterotoxin yields.

Amino Acids↗
PubMed1978

Effect of minerals on staphylococcal enterotoxin B production.

Raising the magnesium level from 0.4 to 1.5 mM in a medium containing only amino acids (2.08%), salts, and vitamins increased enterotoxin B production by Staphylococcus aureus S-6 by about 80%. The level of phosphates in the medium was lowered to one-tenth (to 2.87 mM) the original amount without adversely affecting growth and enterotoxin production. The optimum level of potassium was between 15 and 45 mM. Ammonium salts were not essential in the amino acid medium. Sufficient quantities of trace metals were already present. Revising the salt mixture according to the information obtained resulted in a doubling of the enterotoxin B production.

Enterotoxins↗
PubMed1978

Intracytoplasmic membrane, phospholipid, and sterol content of Methylobacterium organophilum cells grown under different conditions.

Intracytoplasmic membranes were present in Methylobacterium organophilum when cells were grown with methane, but not methanol or glucose, as the sole carbon and energy source. Cells grown with methane as the carbon and energy source and low levels of dissolved oxygen had the greatest amount of intracytoplasmic membrane. Cells grown with increased levels of dissolved oxygen had less intracytoplasmic membrane. The amount of total lipid correlated with the amount of membrane material observed in thin sections. The individual phospholipids varied in amount, but the same four were present in M. organophilum grown with different substrates and oxygen levels. Phosphatidyl choline was present as a major component of the phospholipids. Sterols were present, and they differed from those in the type I methylotroph Methylococcus capsulatus. The relative amounts of different sterols and squalene changed with the substrate provided for growth. The greatest amounts of sterols were found in methane-grown cells grown at low levels of dissolved oxygen. None of the unusual or usual membrane components assayed was uniquely present in the intracytoplasmic membranes.

Membranes↗
PubMed1977

Genetic transformation in Methylobacterium organophilum.

Several mutants have been isolated from the facultative methylotroph, Methylobacterium organophilum, using either N-methyl-N'-nitro-N-nitrosoguanidine or ultraviolet light as mutagens. One of these isolates, a glutamate auxotroph lacking isocitrate dehydrogenase, has been transformed to prototrophy, using wild-type DNA, at a frequency of 0-5%. Competence and DNA uptake occur only in cultures which are near the end of exponential growth, and maximal transformation requires a DNA concentration of 100 mug ml-1.

DNA, Bacterial↗
PubMed1975

Physiology of sporeforming bacteria associated with insects: metabolism of Bacillus popilliae grown in third-instar Popillia japonica Newman larvae.

The timing and relative participation of concurrent pathways of carbohydrate metabolism as well as the extent of terminal respiratory activity were determined by radiorespirometry with 14-C substrates and by enzyme assays for vegetative and sporulating cells of the bacterium Bacillus popilliae cultured in whole, intact Popillia japonica (Japanese beetle) larvae. During vegetative proliferation, the pentose phosphate pathway predominates in the bacterial cells with minor involvement of the Embden-Meyerhof-Parnas pathway. As the cells proceed through sporulation, pentose phosphate and Embden-Meyerhof-Parnas activity remains constant. No tricarboxylic cycle activity is evident during growth and sporulation of B. popilliae. The results demonstrate (i) predominantly aerobic metabolism for carbohydrate assimilation within in vivo sporulating cells, (ii) a major contrast to the metabolism of other aerobic sporeforming bacteria that exhibit derepression of tricarboxylic acid cycle enzymatic activity at the onset of sporulation, and (iii) no causal necessity of the cycle to B. popilliae sporogeny.

Acetates↗
PubMed1975

Regulation of the tricarboxylic acid cycle in gram-positive, facultatively anaerobic bacilli.

The facultative anaerobes Bacillus polymyxa Hino G, B. polymyxa Hino J, and B.macerans were observed to have imcomplete tricarboxylic acid cycles. They were devoid of malate dehydrogenase and all had very low levels of alpha-ketoglutarate dehydrogenase. B. polymyxa Hino J was devoid of alpha-ketoglutarate dehydrogenase when grown aerobically and anerobically. Citrate synthase from B. polymyxa was inhibited by adenosine triphosphate but not reduced nicotinamide adenine dinucleotide and resembled enzymes from other gram-positive bacteria in this respect. Like the citrate synthases from gram-negative, facultative anaerobes and chemolithotrophs, the enzyme from B. polymyxa was inhibited by alpha-ketoglutarate. Inhibition by adenosine triphosphate was shown to be competitive with acetyl-coenzyme A and alpha-ketoglutarate inhibition was competitive with oxaloacetate.

Aconitate Hydratase↗
PubMed1975

Serine transhydroxymethylase isoenzymes from a facultative methylotroph.

Two serine transhydroxymethylase activities have been purified from a facultative methylotrophic bacterium. One enzyme predominates when the organism is grown on methane or methanol as the sole carbon and energy source, whereas the second enzyme is the major isoenzyme found when succinate is used as the sole carbon and energy source. The enzyme from methanol-grown cells is activated by glyoxylate, is not stimulated by Mg2+, Mn2+, or Zn2+, and has four subunits of 50,000 molecular weight each. The enzyme from succinate-grown cells is not activated by glyoxylate and is stimulated by Mg2+, Mn2+, and Zn2+, and sodium dodecyl sulfate-acrylamide gel electrophoresis indicates that this enzyme has subunit molecular weight of 100,000, the same as the molecular weight obtained for the active enzyme. Cells grown in the presence of both methanol and succinate incorporate less methanol carbon per unit time than cells grown on methanol and have a lower specific activity of the glyoxylate-activated enzyme than methanol-grown cells. Adenine, glyoxylate, or trimethoprim in the growth medium causes an increased level of serine transhydroxymethylase in both methanol- and succinate-grown cells by stimulating the synthesis of the glyoxylate-activated enzyme.

Adenine↗
PubMed1975

On the question of integration of Agrobacterium tumefaciens deoxyribonucleic acid by tomato plants.

Treatment of tomato plants with Agrobacterium tumefaciens causes subsequently administered [3H]thymidine to be preferentially incorporated into a satellite deoxyribonucleic acid (DNA) whose buoyant density is between that of bacterial DNA (rho = 1.718 g/cm3) and plant main band DNA (rho = 1.692 g/cm3). Satellite DNA upon shearing or sonic treatment releases fragments of higher and lower buoyant density, as reported by earlier investigators. The satellite has no significant base sequence homology with A. tumefaciens DNA, for its rate of reassociation is not accelerated by the addition of high concentrations of the latter. Tomato DNA isolated from shoots or from leaf nuclei accelerates renaturation of labeled satellite DNA. We conclude that the intermediate density labeled DNA is a plant satellite and not the product of covalent joining of bacterial and plant DNA as suggested by earlier investigators.

Centrifugation, Density Gradient↗
PubMed1974

Adenine nucleotide changes associated with the initiation of sporulation in Bacillus subtilis.

At the end of the exponential growth phase of Bacillus subtilis, there is a decrease in the energy level of the cell, whether expressed as adenosine triphosphate concentration or adenylate energy charge. Phosphate limitation of exponentially growing cells produces a similar decrease in the energy level of the cell, and sporulation is derepressed in the presence of 10 mM glucose. A reduction in the tryptophan concentration of the medium during phosphate limitation of the tryptophan auxotroph B. subtilis 168 prevented the decrease in energy charge. Cells do not sporulate under these conditions. Energy charge values of 0.30 to 0.35 found during sporulation do not lead to cell death.

Adenine Nucleotides↗
PubMed1974

Isolation and characterization of bacteria that grow on methane and organic compounds as sole sources of carbon and energy.

Bacteria capable of growth on methane and a variety of complex organic substrates as sole sources of carbon and energy have been isolated. Conditions used to rigorously establish the purity of the cultures are described. One facultative methylotroph has been studied in detail. This organism has peripherally arranged pairs of intracytoplasmic membranes characteristic of obligate methylotrophs. This isolate apparently utilizes the serine pathway of formaldehyde fixation. The location of methane oxidizers in a dimictic lake indicates that these organisms prefer less than saturating levels of dissolved oxygen. Laboratory experiments confirmed the preference of these organisms for atmospheres containing less oxygen than air.

Anti-Bacterial Agents↗
PubMed1972

Sporulation of tricarboxylic acid cycle mutants of Bacillus subtilis.

A mutant of Bacillus subtilis 168 lacking aconitase (EC 4.2.1.3) was found to be blocked at stage 0 or I of sporulation. Although adenosine triphosphate levels, which normally decrease in tricarboxylic acid cycle mutants at the completion of exponential growth, could be maintained at higher levels by feeding metabolizable carbon sources, this did not permit the cells to progress further into the sporulation sequence. When post-exponential-phase cells of mutants blocked in the first half of the tricarboxylic acid cycle were resuspended with an energy source in culture fluid from post-exponential-phase wild-type B. subtilis or Escherichia coli, good sporulation occurred. The spores produced retained the mutant genotype and were heat stable but lost refractility and heat stability several hours after their production.

Acetates↗
PubMed1971

Isolation and characterization of tricarboxylic acid cycle mutants of Bacillus subtilis.

A technique was developed for the detection, on agar, of mutants of Bacillus subtilis that lacked a functional tricarboxylic acid cycle. Mutants devoid of detectable levels of aconitase, isocitric dehydrogenase, alpha-ketoglutarate dehydrogenase, succinic dehydrogenase, fumarase, and malate dehydrogenase have been isolated and characterized. Several mutants with conditionally expressible lesions, including a mutant with a heat-sensitive citrate synthase, have also been isolated. All of the mutants examined express all the biochemical markers normally absent in early-stage sporulation mutants except elastase, and some of these mutants sporulated nearly as well as the prototroph.

Bacillus subtilis↗