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H O HALVORSON

Publications and source records attributed to H O HALVORSON.

At least 19 recordsLinked to original sources
PubMed1965

REMOVAL OF PLANT NUTRIENTS BY MEANS OF AEROBIC STABILIZATION OF SLUDGE.

In the conventional treatment of sewage, the solids are normally disposed of by anaerobic digestion. This leaves a considerable amount of plant nutrients, such as nitrogen and phosphate, as soluble compounds which will eventually find their way into the plant's final effluent, since the supernatant fluid from the digesters is normally returned to the raw sewage. In a recent investigation, we found that, if the sludges were treated by an aerobic process, a significant portion of the carbonaceous matter was oxidized to carbon dioxide and water, and the rest was assimilated into microbial protoplasm. This process tied up the available nitrogen and phosphorus so that practically none remained dissolved in the suspending liquid. The accumulated solids, consisting mostly of microbial cells, were separated very easily from the liquid, leaving a slightly colored supernatant fluid that was water-clear, free from plant nutrients, and very low in BOD and COD. The overall process was accomplished in a detention time not exceeding 20 days, in contrast to anaerobic digestion which requires from 50 to 70 days.

Chemical Phenomena↗
PubMed1965

KINETICS OF GERMINATION OF BACILLUS SPORES.

Vary, J. C. (University of Wisconsin, Madison), and H. O. Halvorson. Kinetics or germination of Bacillus spores. J. Bacteriol. 89:1340-1347. 1965.-The kinetics of germination of Bacillus cereus strain T spores was accurately described by McCormick. To study the mechanism of germination, it is necessary to correlate the characteristic changes in a population of germinating spores with the behavior of the individual spores in the same population. Two microscopic events are apparent during germination: microlag, the time interval between the addition of l-alanine to heat-activated spores and the beginning of loss in refractility, and microgermination time, the time for the actual change in refractility to occur. The frequency distributions of both events are skewed, and appear to be independent. The effects of l-alanine concentration, heat activation, and temperature of germination on three parameters, microlag, microgermination, and per cent germination, were microscopically studied. The data are discussed in relation to the mechanism of germination, and a correlation between microlag and microgermination times with the constants of McCormick's equation has been suggested.

Alanine↗
PubMed1965

PURIFICATION OF A SALT-REQUIRING ENZYME FROM AN OBLIGATELY HALOPHILIC BACTERIUM.

Holmes, P. K. (University of Illinois, Urbana), and H. O. Halvorson. Purification of a salt-requiring enzyme from an obligately halophilic bacterium. J. Bacteriol. 90: 312-315. 1965.-The discovery that some halophilic enzymes may be reactivated from the salt-free and inactive state has facilitated the purification of nicotinamide adenine dinucleotide-linked malic acid dehydrogenase from crude extracts of Halobacterium salinarium. In the absence of large amounts of salt, the enzyme was totally inactive; yet, in this salt-free state, it could be purified by conventional techniques. The highly purified halophilic enzyme was shown to require a high concentration of salt for activity.

Acetone↗
PubMed1965

PROPERTIES OF A PURIFIED HALOPHILIC MALIC DEHYDROGENASE.

Holmes, P. K. (University of Illinois, Urbana), and H. Orin Halvorson. Properties of a purified halophilic malic dehydrogenase. J. Bacteriol. 90:316-326. 1965.-The malic dehydrogenase (MDH) from Halobacterium salinarium required high concentrations of monovalent ions for stability and activity. Studies of inactivation rates at different salt concentrations suggested that approximately 25% NaCl (w/v) is required to stabilize MDH. From 50 to 100% reactivation, depending on the salt concentration present during inactivation, could occur in 2.5 to 5 m NaCl or KCl. The optimal salt concentration for activity of MDH was a function of the pH, and ranged from 1 to 3 m NaCl or KCl. The effect of salt concentration on the pH-activity curves occurred chiefly below pH 7.0. Inactivation of MDH with heat or thiol reagents showed that the enzyme was more labile in the state induced by absence of salt. The activation of MDH by salts was attributed to a decreased rate of dissociation of MDH and reduced nicotinamide adenine dinucleotide (NADH(2)). The inactivation of the enzyme in the absence of salt could be largely prevented by the presence of NADH(2). The S(20.w) of MDH decreased threefold at low salt concentrations. The enzyme was assumed to be in its native compact configuration only in the presence of a high concentration of salt.

Buffers↗
PubMed1964

PURIFICATION AND PROPERTIES OF L-ALANINE DEHYDROGENASE FROM VEGETATIVE CELLS OF BACILLUS CEREUS.

McCormick, Neil G. (University of Wisconsin, Madison), and Harlyn O. Halvorson. Purification and properties of l-alanine dehydrogenase from vegetative cells of Bacillus cereus. J. Bacteriol. 87:68-74. 1964.-The l-alanine dehydrogenase from vegetative cells of Bacillus cereus strain T has been purified approximately 200-fold. The enzyme has a molecular weight of 248,000 and a turnover number of 80,000 moles of substrate per min per mole of enzyme. The Michaelis constants for the substrates and the equilibrium constant for the reaction catalyzed by this enzyme are in close agreement with reported values for other l-alanine dehydrogenases. The kinetic properties of the enzyme purified from vegetative cells are identical to those of the enzyme isolated from spores of the same organism, but differ with respect to relative heat stability. Whereas spores contain a heat-resistant enzyme, vegetative cells contain, in addition, a heat-sensitive enzyme. No evidence was found to support the hypothesis that a molecular conversion type of phenomenon plays a role in the appearance of spore enzyme.

Alanine↗
PubMed1964

ACTIVATION OF BACTERIAL ENDOSPORES.

A. Keynan (Israel Institute of Biological Research, Ness Ziona, Israel), Z. Evenchik, H. O. Halvorson, and J. W. Hastings. Studies on the activation of bacterial endospores. J. Bacteriol. 88:313-318. 1964.-Heat activation of bacterial endospores was imitated by suspending spores in reducing agents (mercaptoethanol or thioglycolate) or in a pH less than 4.5. Urea (6 m) had no effect on spores. In addition to the well-known activation at 65 C for 45 min, spores were also activated by exposure to 34 C for 48 hr. The activation by heat and by reducing agents was reversible; the reverse reaction was temperature-dependent. No reversion occurred at -20 C, whereas at 28 C the spores reversed to their original dormant state within 72 hr. It is suggested that the heat-activation phenomenon could be explained by assuming that heat or reducing agents change the tertiary structure of a protein responsible for the maintenance of the dormant state by reducing the disulfide linkages which stabilize the protein in a specific configuration. The partial denaturation of this protein is reversible by reoxidation of the reduced disulfide bonds.

Acid-Base Equilibrium↗
PubMed1964

ENDOGENOUS FACTOR IN SPOROGENESIS IN BACTERIA. II. GROWTH AND SPORULATION IN BACILLUS SUBTILIS.

Kerravala, Zarrine J. (University of Illinois, Urbana), V. R. Srinivasan, and H. Orin Halvorson. Endogenous factor in sporogenesis in bacteria. II. Growth and sporulation of Bacillus subtilis. J. Bacteriol. 88:374-380. 1964.-The presence of an endogenous factor in Bacillus subtilis which could initiate sporogenesis in suspensions of washed vegetative cells was demonstrated. The inability to obtain a culture of vegetative cells, relatively free from spores, by the "active culture" technique necessitated the use of the "continuous culture" method. The investigations on the continuous cultivation of this organism, to obtain a steady-state population of actively growing vegetative cells, resulted in certain observations which gave an insight into the nature of sporogenesis. Growth studies of the organism under these conditions showed that there was a rise in viable cell numbers, until a maximal population was reached. This was maintained at a steady-state level for sometime; on further incubation, there was a reduction in cell numbers, and consequently the steady state could not be maintained any longer. Spore counts showed that the spore fraction of the total population increased on prolonged incubation. The commitment to sporulation appeared to have caused a reduction in the growth rate of the population, which was experimentally demonstrated by a decline in cell numbers. In contrast, when B. cereus strain T. was grown as a continuous culture, it could be maintained as a steady-state population of vegetative cells, for longer periods, like a nonsporeformer (e.g., Escherichia coli). This difference in behavior could be attributed to the fact that whereas B. subtilis can sporulate in the presence of nutrients, B. cereus strain T. cannot do so until the medium has been depleted of nutrients.

Bacillus cereus↗
PubMed1963

Biochemistry of sporulation. I. Metabolism of acetate by vegetative and sporulating cells.

Hanson, Richard S. (University of Illinois, Urbana), V. R. Srinivasan, and H. Orin Halvorson. Biochemistry of sporulation. I. Metabolism of acetate by vegetative and sporulating cells. J. Bacteriol. 85:451-460. 1963.-The transition from the vegetative to the sporulating cycle in a sporeformer is marked by a change in the enzymatic machinery of the cell. When vegetative cells of Bacillus cereus strain T are grown in a glucose-yeast extract-minerals medium, acetate accumulates until the beginning of the sporulation cycle. The acetate-activating systems are present in the vegetative cells as well as in the cells of the early stages of sporulation, whereas the enzymes necessary for the terminal oxidation of acetate to carbon dioxide are absent in the vegetative stage. The induction of a functional tricarboxylic acid cycle during early sporulation is inhibited by chloramphenicol. alpha-Picolinic acid also prevents morphological, as well as physiological, changes during the transition.

Acetates↗
PubMed1963

BIOCHEMICAL CHANGES OCCURRING DURING SPORULATION OF BACILLUS CEREUS T. II. EFFECT OF ESTERS OF ORGANIC ACIDS ON SPORULATION.

Gollakota, K. G. (University of Illinois, Urbana) and H. Orin Halvorson. Biochemical changes occurring during sporulation of Bacillus cereus T. II. Effect of esters of organic acids on sporulation. J. Bacteriol. 85:1386-1393. 1963.-Sporulation of Bacillus cereus T in yeast extract-glucose-minerals medium was specifically inhibited by alpha-picolinic acid (APA), if the acid was added before the pH of the culture began to rise. The effects of APA could be reversed by aspartic acid or asparagine, among the amino acids, and by intermediates of the tricarboxylic acid cycle, with the exception of alpha-ketoglutarate and fumarate. Formate, malonate, and certain other organic acids also possessed this ability. Succinate was the best reversing agent. Fluoroacetic acid (FAA) also inhibited sporulation, but had no effect on vegetative growth or germination of spores of B. cereus T. Unlike APA, FAA inhibited sporulation even when added after the pH of the culture had started to rise. Bisulfite was similar to FAA in its effects on sporulation. With the exception of pyruvate, acetate, aspartate, and malate, most of the compounds reversing the effects of APA also overcame the effects of FAA or bisulfite on sporulation. Esters of some of the acids reversing the effects of the above inhibitors were studied for their action on germination, growth, and sporulation. Ethyl pyruvate prevented germination of the spores, slowed down growth, and inhibited sporulation. Ethyl malonate and ethyl succinate inhibited only sporulation. All the above inhibitors prevented the synthesis of dipicolinic acid (DPA) also. When B. cereus T was grown in the absence of glucose (in extracted yeast extract-minerals medium), the above inhibitors had no effect on sporulation. Ethyl oxamate permitted sporulation, but the spores produced were heat-sensitive. Ethyl pimelate caused lysis when added before the pH of the culture began to rise. When added after the pH of the culture began to rise, it also permitted sporulation, and the spores were sensitive to heat. (These heat-sensitive spores were refractile and dormant, and did not stain with crystal violet. However, they germinated normally, losing refractibility and became stainable.) The effect of ethyl oxamate and ethyl pimelate could be overcome by DPA. APA, FAA, ethyl malonate, and ethyl succinate also inhibit the sporulation of a number of other bacilli.

Amino Acids↗
PubMed1963

BIOCHEMISTRY OF SPORULATION. II. ENZYMATIC CHANGES DURING SPORULATION OF BACILLUS CEREUS.

Hanson, Richard S. (University of Illinois, Urbana), V. R. Srinivasan, and H. Orin Halvorson. Biochemistry of sporulation. II. Enzymatic changes during sporulation of Bacillus cereus. J. Bacteriol. 86:45-50. 1963.-It has been possible to correlate enzymatic activities of Bacillus cereus strain T with particular phases of growth and sporulation by using cultures in which the cells grow rapidly and undergo the transition from growth to sporulation in a synchronous manner. Cells harvested during vegetative growth lack a functional tricarboxylic acid cycle, and the enzymes required for the completion of this cycle are synthesized during the transition from growth to sporulation. alpha-Picolinic acid, a specific antisporogenic agent, prevented the synthesis of aconitase. Its effect on aconitase synthesis was reversed by agents capable of reversing its inhibition of sporulation, and, therefore, its antisporogenic activity is believed to be related to its ability to prevent the formation of an active tricarboxylic acid cycle, which is required for sporulation but not growth.

Bacillus cereus↗
PubMed1963

COMPARISON OF THE ACTIVE TRANSPORT SYSTEMS FOR ALPHA-THIOETHYL- D-GLUCOPYRANOSIDE AND MALTOSE IN SACCHAROMYCES CEREVISIAE.

Okada, Hirosuke (University of Wisconsin, Madison), and H. O. Halvorson. Comparison of the active transport systems for alpha-thioethyl-d-glucopyranoside and maltose in Saccharomyces cerevisiae. J. Bacteriol. 86:966-970. 1963.-Inducible systems for the active transport of both maltose and alpha-thioethyl-d-glucopyranoside (alpha-TEG) have been described in strains of Saccharomyces cerevisiae. The properties of induction of the alpha-TEG-accumulating system were similar to other inducible systems in yeast: the differential rate of synthesis was constant, and induction was inhibited by amino acid analogues. At temperatures below 20 C, the temperature dependence of alpha-TEG accumulation in induced cells was identical to that in facilitated diffusion. From a survey of various inducers, a coordinate induction of both active-transport systems was observed. These findings led to the conclusion that in active transport a common inducible enzyme is coupled to both the alpha-TEG and maltose facilitated-diffusion systems.

Biological Transport↗