Exogenous Glucose Concentration Research Articles

The Effect of Carbohydrate and Nitrogen Concentration on Phenol Synthesis in Paul's Scarlet Rose Cells Grown in Tissue Culture

AbstractThe effects of exogenous concentrations of glucose and nitrate on total ethanol extractable phenols and leucoanthocyanins were studied in Paul's Scarlet Rose cells grown in either liquid suspension or solid culture. Aliquots of liquid suspension cultured cells were harvested during logarithmic, early stationary, and late stationary periods of growth for determination of fresh weight, dry weight, total ethanol extractable phenols and leucoanthocyanins. Cells produced phenols during all phases of growth, but at stationary phase, the production was greatest. Increasing concentrations of exogenous glucose in the culture medium resulted in an increased synthesis of total phenols in logarithmic cells, and an increased synthesis of total phenols and leucoanthocyanin in stationary cells. Addition of increased concentrations of exogenous nitrate to the stationary cells grown in suspension culture markedly reduced synthesis of leucoanthocyanins although total phenol synthesis was not significantly affected. Similar observations were made in cells cultured on solid medium in respect to exogenous glucose concentration, however these cells differed from the suspension cultured cells by having increased amounts of total phenol synthesis and decreased synthesis of leucoanthocyanins in the presence of increasing concentrations of exogenous nitrate in the culture medium.

A levansucrase from Actinomyces viscosus.

The present study deals with the production and properties of a fructosyltransferase from Actinomyces viscosus which was found to be an extracellular enzyme. In batch and in continuous cultures, the enzyme activity was low at high exogenous glucose concentration. This relationship may be indirect and result from secondary effects such as the production of inhibitory substances or proteolytic enzymes or, in the case of batch cultures, by retardation of growth. The properties of fructosyltransferase from A. viscosus were similar to those described for fructosyltransferases from other bacterial species.

The existence of two membrane transport systems for glucose in suspensions of sugarcane cells

Summary Transport of glucose in sugarcane cells depends upon the prior history of cell incubation. High concentrations of glucose suppress a transport mechanism characterized by high affinity for the cells, insensitivity to the presence of F−, and saturation of the system at 100–200 μM exogenous glucose. This system (System A) becomes expressed when glucose concentration in the medium is kept below 0.1% (5.6 mM). System B is characteristic of cells grown in high glucose concentrations. It has low affinity for the cells, is inhibited by F−,, and saturates at about 1 mM exogenous glucose concentration. Repression of System A occurs in a few minutes while its derepression requires about 7 hr. Cycloheximide and anisomycin inhibit derepression of System A.

Synthesis and degradiation of intracellular polyglucose in Streptococcus salivarius.

The incorporation of large quantities of glucose into an intracellular polymer similar in composition to glycogen has been demonstrated with growing and resting cells of Streptococcus salivarius isolated from human saliva. Characteristics of the synthetic process have been determined with resting cells grown in minimal glucose broth and then incubated with glucose-14C in a nitrogen-free buffer medium. At an optimum pH of 7.0, cells rapidly synthesized large quantities of intracellular polyglucose incorporating glucose at an initial rate of 5.6 μmoles/h per mg dry weight of cells. At exogenous glucose concentrations of 11.0 μmoles per milligram dry cells or above, resting cells would not incorporate more than 2.75 μmoles of glucose into intracellular polysaccharide. The incorporation of this amount of glucose represents a 50% increase in cell size on a dry weight basis and reflects the physical limit of these cells without cell division. Almost 90% of this intracellular material was utilizable glucose in polymer form with the remaining material being incorporated into structural components. The enzymes for polyglucose synthesis were found to be constitutive, although the rate and degree of synthesis was reduced after prolonged exposure to carbon sources other than glucose, possibly reflecting an alteration in the glucose transport system. Growth at high levels of glucose also suppressed the rate of polyglucose synthesis as well as the rate of glucose utilization. Rapid degradation of the intracellular polyglucose was always observed in the absence of exogenous carbohydrate with the last molecules of glucose synthesized into the polymer being the first to be degraded upon exhaustion of the exogenous glucose. With resting cells of S. salivarius, the exogenous glucose not incorporated into polyglucose was stoichiometrically converted to lactic acid, but only 80–85% of the endogenous polyglucose was converted to this end-product in the absence of exogenous glucose, with the remaining 15–20% being degraded to small amounts of α-ketoglutarate, citrate, pyruvate, and an unknown acid. In this organism, intracellular polyglucose synthesis and degradation appear to be controlled processes, as experiments designed to measure the specific activity of lactic acid, produced by cells grown on high and low levels of glucose and metabolizing radioactive glucose, have shown that synthesis and degradation of intracellular polyglucose do not proceed simultaneously.

Influence of exogenous substrates on the endogenous respiration of Pseudomonas aeruginosa.

Gronlund, Audrey F. (University of British Columbia, Vancouver, Canada), and J. J. R. Campbell. Influence of exogenous substrates on the endogenous respiration of Pseudomonas aeruginosa. J. Bacteriol. 91:1577-1581. 1966.-The influence of growth conditions, ammonium ions, and glucose concentration on endogenous respiration in Pseudomonas aeruginosa was determined by measuring C(14)O(2) evolution from uniformly labeled cells that had previously been grown on C(14)-glucose. A 93% suppression of endogenous C(14)O(2) evolution was evident under growth conditions, and a 66% suppression was observed in the presence of excess glucose. Increasing exogenous glucose concentrations supported decreasing levels of endogenous C(14)O(2) evolution. Ammonium ions slightly suppressed endogenous activity and enhanced the decrease in C(14)O(2) release observed with exogenous glucose. In addition, the effect of exogenous glucose, alpha-ketoglutarate, 2-ketogluconate, aspartic acid, and adenosine selectively on both endogenous ribonucleic acid (RNA) and protein oxidation was followed by measuring C(14)O(2) evolution from cells grown with C(14)-uracil or C(14)-proline. The five exogenous substrates examined suppressed endogenous RNA oxidation, and the degree of suppression appeared to be correlated with the amount of oxygen consumption and, hence, energy gained during the oxidation of these substrates. Oxidation of endogenous protein was decreased when cells were incubated with glucose, aspartate, and adenosine, but was increased when alpha-ketoglutarate and 2-ketogluconate were the exogenous substrates. The influence of the oxidizable exogenous compounds appeared to be related, in part, to the ammonium ion requirement imposed upon the cells for assimilation of the individual exogenous substrate.

Studies in vivo on hexose metabolism in Dictyostelium discoideum

During differentiation of D. discoideum, the intracellular concentrations of glucose and UDPG change, peaking at the culmination stage. Experiments using 1- and 6-C 14-glucose have shown that the exogenous glucose concentration affects the relative rates of C 14O 2 evolution from 1- and 6-C 14-glucose. These studies have led to the conclusion that the changing hexose levels occurring during development also exert an influence on the pathways of hexose metabolism.

The effect of exogenous glucose concentration of C-6/C-1 ratio

The effect of exogenous glucose concentration of C-6/C-1 ratio