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Biomedical subjects

C D Taylor

Publications and source records attributed to C D Taylor.

At least 37 records · Page 2Linked to original sources
PubMed1985

Passive diffusion technique for concentration of short-chain volatile Fatty acids from seawater.

A diffusion chamber is described which concentrates short-chain, volatile fatty acids from seawater while simultaneously separating them from interfering salts. The procedure relies on the passive diffusion of volatile compounds from acidified seawater samples and their subsequent absorption onto a base-impregnated filter. The method is simple, efficient, and adaptable to most commonly used methods of volatile acid analysis.

Journal Article↗
PubMed1982

Assimilatory Sulfur Metabolism in Marine Microorganisms: Sulfur Metabolism, Protein Synthesis, and Growth of Alteromonas luteo-violaceus and Pseudomonas halodurans During Perturbed Batch Growth.

The antibiotic protein synthesis inhibitor chloramphenicol specifically blocked the incorporation of [S]sulfate into the residue protein of two marine bacteria, Pseudomonas halodurans and Alteromonas luteo-violaceus. Simultaneous inhibition of total protein synthesis occurred, but incorporation of S into low-molecular-weight organic compounds continued. A. luteo-violaceus rapidly autolyzed, with similar reduction in cell counts, total culture protein and cellular sulfur, whereas P. halodurans remained viable. Treatment with chloramphenicol, growth during nitrogen and carbon limitation, and the carbon and energy sources used for growth did not alter the sulfur content of P. halodurans protein. The mean value (1.09%, by weight), representing a wide variety of environmentally relevant growth conditions, was in agreement with model protein composition. The variability of cellular composition of P. halodurans and A. luteo-violaceus is discussed with respect to the measurement of bacterial growth in natural environments. Total carbon and nitrogen per cell varied greatly (coefficient of variation, ca. 100%) depending on growth conditions. Variation in total sulfur and protein per cell was much less (coefficient of variation, <50%), but the least variation was found for sulfate incorporation into residue protein (coefficient of variation, ca. 15%). Thus, sulfate incorporation into residue protein can be used as an accurate measurement of de novo protein synthesis in these bacteria.

Journal Article↗
PubMed1982

Assimilatory sulfur metabolism in marine microorganisms: considerations for the application of sulfate incorporation into protein as a measurement of natural population protein synthesis.

The sulfur content of residue protein was determined for pure cultures of Nitrosococcus oceanus, Desulfovibrio salexigens, 4 mixed populations of fermentative bacteria, 22 samples from mixed natural population enrichments, and 11 nutritionally and morphologically distinct isolates from enrichments of Sargasso Sea water. The average 1.09 +/- 0.14% (by weight) S in protein for 13 pure cultures agrees with the 1.1% calculated from average protein composition. An operational value encompassing all mixed population and pure culture measurements has a coefficient of variation of only 15.1% (n = 41). Short-term [S]sulfate incorporation kinetics by Pseudomonas halodurans and Alteromonas luteoviolaceus demonstrated a rapid appearance of S in the residue protein fraction which was well modelled by a simple exponential uptake equation. This indicates that little error in protein synthesis determination results from isotope dilution by endogenous pools of sulfur-containing compounds. Methionine effectively competed with sulfate for protein synthesis in P. halodurans at high concentrations (10 muM), but had much less influence at 1 muM. Cystine competed less effectively with sulfate, and glutathione did not detectably reduce sulfate-S incorporation into protein. [S]sulfate incorporation was compared with [C]glucose assimilation in a eutrophic brackish-water environment. Both tracers yielded similar results for the first 8 h of incubation, but a secondary growth phase was observed only with S. Redistribution of C from low-molecular-weight materials into residue protein indicated additional protein synthesis. [S]sulfate incorporation into residue protein by marine bacteria can be used to quantitatively measure bacterial protein synthesis in unenriched mixed populations of marine bacteria.

Journal Article↗
PubMed1981

Technique for simultaneous determination of [s]sulfide and [C]carbon dioxide in anaerobic aqueous samples.

A technique for the simultaneous determination of [S]sulfide and [C]carbon dioxide produced in anaerobic aqueous samples dual-labeled with [S]sulfate and a C-organic substrate is described. The method involves the passive distillation of sulfide and carbon dioxide from an acidified water sample and their subsequent separation by selective chemical absorption. The recovery of sulfide was 93% for amounts ranging from 0.35 to 50 mumol; recovery of carbon dioxide was 99% in amounts up to 20 mumol. Within these delineated ranges of total sulfide and carbon dioxide, 1 nmol of [S]sulfide and 7.5 nmol of [C]carbon dioxide were separated and quantified. Correction factors were formulated for low levels of radioisotopic cross-contamination by sulfide, carbon dioxide, and volatile organic acids. The overall standard error of the method was +/-4% for sulfide and +/-6% for carbon dioxide.

Journal Article↗
PubMed1981

Assimilatory sulfur metabolism in marine microorganisms: characteristics and regulation of sulfate transport in Pseudomonas halodurans and Alteromonas luteo-violaceus.

Sulfate transport capacity was not regulated by cysteine, methionine, or glutathione in Pseudomonas halodurans, but growth on sulfate or thiosulfate suppressed transport. Subsequent sulfur starvation of cultures grown on all sulfur sources except glutathione stimulated uptake. Only methionine failed to regulate sulfate transport in Alteromonas luteo-violaceus, and sulfur starvation of all cultures enhanced transport capacity. During sulfur starvation of sulfate-grown cultures of both bacteria, the increase in transport capacity was mirrored by a decrease in the low-molecular-weight organic sulfur pool. Little metabolism of endogenous inorganic sulfate occurred. Cysteine was probably the major regulatory compound in A. luteo-violaceus, but an intermediate in sulfate reduction, between sulfate and cysteine, controlled sulfate transport in P. halodurans. Kinetic characteristics of sulfate transport in the marine bacteria were similar to those of previously reported nonmarine systems in spite of significant regulatory differences. Sulfate and thiosulfate uptake in P. halodurans responded identically to inhibitors, were coordinately regulated by growth on various sulfur compounds and sulfur starvation, and were mutually competitive inhibitors of transport, suggesting that they were transported by the same mechanism. The affinity of P. halodurans for thiosulfate was much greater than for sulfate.

Bacteria↗
PubMed1981

Assimilatory sulfur metabolism in marine microorganisms: a novel sulfate transport system in Alteromonas luteo-violaceus.

The sulfate transport mechanism of a marine bacterium, Alteromonas luteo-violaceus, was unique among microorganisms in its extremely low affinity for the sulfate analog thiosulfate. Distinguishing characteristics included weak inhibition of sulfate transport by thiosulfate, inability to transport thiosulfate effectively, poor growth using thiosulfate as the sole source of sulfur, and a mild effect of the sulfhydryl reagent para-hydroxymercuribenzoate. In contrast, sulfate transport by a marine pseudomonad, Pseudomonas halodurans, was strongly inhibited by thiosulfate, and para-hydroxymercuribenzoate reversibly but completely blocked sulfate transport.

Bacteria↗
PubMed1979

Growth of a bacterium under a high-pressure oxy-helium atmosphere.

Growth of a barotolerant marine organism, EP-4, in a glutamate medium equilibrated with an oxy-helium atmosphere at 500 atmospheres (atm; total pressure) (20 degrees C) was compared with control cultures incubated at hydrostatic pressures of 1 and 500 atm. Relative to the 1-atm control culture, incubation of EP-4 at 500 atm in the absence of an atmosphere resulted in an approximately fivefold reduction in the growth rate and a significant but time variant reduction in the rate constants for the incorporation of substrate into cell material and respiration. Distinct from the pressurized control and separate from potential effects of dissolution of helium upon decompression of subsamples, exposure of the organism to high-pressure oxy-helium resulted in either a loss of viability of a large fraction of the cells or the arrest of growth for one-third of the experimental period. After these initial effects, however, the culture grew exponentially at a rate which was three times greater than the 500-atm control culture. The rate constant for the incorporation of substrate into cell material was also enhanced twofold in the presence of high-pressure oxy-helium. Dissolved oxygen was well controlled in all of the cultures, minimizing any potential toxic effects of this gas.

Journal Article↗
PubMed1979

Solubility of oxygen in a seawater medium in equilibrium with a high-pressure oxy-helium atmosphere.

The molar oxygen concentration in a seawater medium in equilibrium with a high-pressure oxygen-helium atmosphere was measured directly in pressurized subsamples, using a modified version of the Winkler oxygen analysis. At a partial pressure of oxygen of 1 atm or less, its concentration in the aqueous phase was adequately described by Henry's Law at total pressures up to 600 atm. This phenomenon, which permits a straightforward determination of dissolved oxygen within hyperbaric systems, resulted from pressure-induced compensatory alterations in the Henry's Law variables rather than from a true obedience to the Ideal Gas Law. If the partial pressure of a gas contributes significantly to the hydrostatic pressure, Henry's Law is no longer adequate for determining its solubility within the compressed medium.

Atmospheric Pressure↗
PubMed1978

Comparison of respirable coal mine dust concentrations measured with an MRE and a newly-developed, two-stage impactor sampler.

The design and laboratory evaluation of a two-stage aerosol sampler using an impaction plate for removing particles above 10 micron, has been reported. The unit was developed to provide an alternative to the two-stage sampling head used on approved coal mine personal respirable dust samplers. The new device offers the potential of increasing the analytical accuracy of samples, and of providing a device more suitable to the mining community for use in their mandated dust sampling program. This paper describes the underground sampling program conducted to establish the factor for converting respirable dust concentrations measured with this device to equivalent concentrations measured with an Isleworth 113A gravimetric dust sampler (MRE). This study demonstrated that the use of the impactor sampling head provides a viable alternative to the currently used sampling head. The results showed that comparative measurements could be linearly related for MRE dust measurements ranging from 0.5 to 5.5 mg/m3. The factor determined for converting measurements made with the new head to equivalent MRE measurements was approximately 0.5.

Coal↗
PubMed1976

Subsampling technique for measuring growth of bacterial cultures under high hydrostatic pressure.

A method is presented for measuring growth of bacteria under high hydrostatic pressure in subsamples taken without pressure change in the incubation vessel. Subsamples may be withdrawn rapidly (5 s) and are not subjected to shear forces. Vice versa, nutrient media, labeled substrates, etc., may be introduced into the culture while under pressure. Chemical fixation of subsamples for electron microscopy or adenosine 5'-triphosphate determinations under pressure is also possible without affecting the growing culture. Data are given of growth experiments demonstrating the feasibility of the method. Problems of oxygen depletion are discussed.

Bacteria↗
PubMed1976

Undecompressed microbial populations from the deep sea.

Metabolic transformations of glutamate and Casamino Acids by natural microbial populations collected from deep waters (1,600 to 3,100 m) were studied in decompressed and undecompressed samples. Pressure-retaining sampling/incubation vessels and appropriate subsampling/incubation vessels and appropriate subsampling techniques permitted time course experiments. In all cases the metabolic activity in undecompressed samples was lower than it was when incubated at 1 atm. Surface water controls showed a reduced activity upon compression. The processes involving substrate incorporation into cell material were more pressure sensitive than was respiration. The low utilization of substrates, previously found by in situ incubations for up to 12 months, was confirmed and demonstrated to consist of an initial phase of activity, in the range of 5 to 60 times lower than the controls, followed by a stationary phase of virtually no substrate utilization. No barophilic growth response (higher rates at elevated pressure than at 1 atm) was recorded; all populations observed exhibition various degrees of barotolerance.

Amino Acids↗
PubMed1974

Biosynthetic dihydroorotate dehydrogenase from Lactobacillus bulgaricus: partial characterization of the enzyme.

Some of the catalytic properties of the biosynthetic dihydroorotate dehydrogenase purified from an anaerobic bacterium, Lactobacillus bulgaricus, are described. Studies with p-hydroxymercuribenzoate, N-ethylmaleimide, and mercuric chloride showed that sulfhydryl groups are necessary for transfer of electrons from dihydroorotate to a variety of electron acceptors. Protection studies with substrates for the enzyme indicated that free sulfhydryl groups at or near the active center are required for catalytic activity. Evidence is presented for the production of superoxide free radicals during reaction of the enzyme with molecular oxygen. Inhibitor studies with Tiron indicated that reduction of cytochrome c by the enzyme may involve the superoxide free radical as an intermediate. Orotate, one of the substrates for the enzyme, has been found to be a competitive inhibitor for the dihydroorotate site. The K(i) for orotate as estimated by several techniques is 0.1 mM. The K(m) for dihydroorotate with ferricyanide as the electron acceptor is estimated to be 0.5 mM.

Anaerobiosis↗