Glycogen biosynthesis via UDP-glucose in the ruminal bacterium Prevotella bryantii B1(4).

Prevotella bryantii is an important amylolytic bacterium in the rumen that produces considerable amounts of glycogen when it is grown on maltose. Radiolabel studies indicated that glucose-1-phosphate was converted to UDP-glucose, and this latter intermediate served as the immediate precursor for glycogen synthesis. High levels of UDP-glucose pyrophosphorylase activities (> 1,492 nmol/min/mg of protein) were detected in cells grown on maltose, cellobiose, glucose, or sucrose, and activity was greatly stimulated (by approximately 60-fold) by the addition of fructose-1,6-bis phosphate (half-maximal activation concentration was 240 microM). However, ADP-glucose pyrophosphorylase activity was not detected in any of the cultures. Glycogen synthase activity in maltose-grown cultures (48 nmol/min/mg of protein) was higher than that in cellobiose-, sucrose-, and glucose-grown cultures (< 26 nmol/min/mg of protein). This is the first report of a bacterium that exclusively uses UDP-glucose to synthesize glycogen. The elucidation of this unique glycogen biosynthesis pathway provides information necessary to further investigate the role of bacterial glycogen accumulation in rumen metabolism.     

Some aspects of catabolite repression of mitochondrial enzymes inSaccharomyces cerevisiae

The synthesis of mitochondrial enzymes inSaccharomyces cerevisiae is partly derepressed during growth with maltose as compared with glucose. The present investigations were aimed at finding any more differences between maltose- and glucose-grown cultures that might indicate the nature of the effector(s) of catabolite repression.The capacity of the pentose-phosphate pathway in resting cells is the same whether they have been grown on maltose or on glucose; about 9% of the sugar is metabolized via this pathway. The activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase are the same in both cultures. There is, however, a correlation between the repression of aconitase synthesis by glucose and the intracellular level of glucose-6-phosphate.There are no differences between maltose- and glucose-grown cultures in the concentration of structural and reserve carbohydrates, RNA and proteins, except for glycogen. In young maltose-grown cultures the level of this polysaccharide is about 25% higher.The growth rate and the rate of sugar consumption per mg of cells in maltose-grown cultures are about 30% lower than in glucose-grown cultures. Probably the restriction of sugar consumption in maltose-grown cultures results in less accumulation of catabolites and in partial derepression of the synthesis of mitochondrial enzymes.The author is much indebted to Mrs. M. Vermeulen-Verdam for her skillful and enthusiastic assistance. He also thanks Mr. J. H. M. Bex, Mr. L. van Dijk, Mr. E. A. H. Huisman and Mr. A. de Wit for their cooperation in some parts of the present work.     

Purification and characterization of two phosphoglucomutases from Lactococcus lactis subsp. lactis and their regulation in maltose- and glucose-utilizing cells.

Two distinct forms of phosphoglucomutase were found in Lactococcus lactis subsp. lactis, strains 19435 and 65.1, growing on maltose: beta-phosphoglucomutase (beta-PGM), which catalyzes the reversible conversion of beta-glucose 1-phosphate to glucose 6-phosphate in the maltose catabolism, and alpha-phosphoglucomutase (alpha-PGM). beta-PGM was purified to more than 90% homogeneity in crude cell extract from maltose-grown lactococci, and polyclonal antisera to the enzyme were prepared. The molecular mass of beta-PGM was estimated by gel filtration to be 28 kDa; its isoelectric point was 4.8. The corresponding values for alpha-PGM were 65 kDa and 4.4, respectively. The expression of both PGM enzymes was investigated under different growth conditions. The specific activity and amount of beta-PGM per milliliter of cell extract increased with time in lactococci grown on maltose, but the enzyme was absent in lactococci grown on glucose, indicating enzyme synthesis to be induced by maltose in the growth medium. When glucose was added to maltose-grown lactococci, both the specific activity and amount of beta-PGM per milliliter of cell extract decreased rapidly. This suggests that synthesis of beta-PGM is repressed by glucose in the medium. Although the specific activity of alpha-PGM did not change during growth on maltose or glucose, lactococcal strain 19435 showed a much higher specific activity of both alpha- and beta-PGM than strain 65.1 when grown on maltose.     

beta-Glucose-1-Phosphate, a Possible Mediator for Polysaccharide Formation in Maltose-Assimilating Lactococcus lactis

Homolactic fermentation of glucose and heterolactic fermentation of maltose with Lactococcus lactis 65.1 were confirmed. When moles of glucose were compared, the uptake rates of the two carbon sources were similar. The intracellular concentration of fructose-1,6-diphosphate (FDP) in maltose-assimilating cells was half of that in glucose-assimilating cells. Similarly, formation of FDP and lactate from maltose by extracts of maltose-grown cells was half of that formed from glucose by extracts of glucose-grown cells, indicating a difference in the utilization of the two carbon sources for energy metabolism. Concentrations of adenine nucleotides were similar in both types of cells. Glucose-1-phosphate was found in extracts of maltose-grown cells given maltose and, in addition, an inducible and low beta-specific phosphoglucomutase activity was observed. beta-Glucose-1-phosphate was not metabolized by cell extracts to either FDP or lactate, suggesting an alternative metabolic route. The amount of [C]maltose incorporated into the cell material of maltose-grown cells was four times greater than that of [C]glucose incorporated into the cell material of glucose-grown cells. The intracellular concentration of UTP was lower in maltose-assimilating cells than in glucose-assimilating cells. Cells grown on maltose were more spherical and less fragile than cells grown on glucose.     

β-Glucose-1-Phosphate, a Possible Mediator for Polysaccharide Formation in Maltose-Assimilating Lactococcus lactis

Homolactic fermentation of glucose and heterolactic fermentation of maltose with Lactococcus lactis 65.1 were confirmed. When moles of glucose were compared, the uptake rates of the two carbon sources were similar. The intracellular concentration of fructose-1,6-diphosphate (FDP) in maltose-assimilating cells was half of that in glucose-assimilating cells. Similarly, formation of FDP and lactate from maltose by extracts of maltose-grown cells was half of that formed from glucose by extracts of glucose-grown cells, indicating a difference in the utilization of the two carbon sources for energy metabolism. Concentrations of adenine nucleotides were similar in both types of cells. Glucose-1-phosphate was found in extracts of maltose-grown cells given maltose and, in addition, an inducible and low β-specific phosphoglucomutase activity was observed. β-Glucose-1-phosphate was not metabolized by cell extracts to either FDP or lactate, suggesting an alternative metabolic route. The amount of [¹⁴C]maltose incorporated into the cell material of maltose-grown cells was four times greater than that of [¹⁴C]glucose incorporated into the cell material of glucose-grown cells. The intracellular concentration of UTP was lower in maltose-assimilating cells than in glucose-assimilating cells. Cells grown on maltose were more spherical and less fragile than cells grown on glucose.     

Glucose and Fructose Metabolism in a Phosphoglucoisomeraseless Mutant of Saccharomyces cerevisiae

A mutant of Saccharomyces cerevisiae deficient in phosphoglucoisomerase (EC 5.3.1.9) is described. It does not grow on glucose or sucrose but does grow on galactose or maltose. Addition of glucose to cultures growing on fructose, mannose, or acetate arrests further growth without altering viability; removal of glucose permits resumption of growth. Glucose causes accumulation of nearly 30 mumoles of glucose-6-phosphate per g (wet weight) of cells and suppresses synthesis of ribonucleic acid. Inhibition of growth by glucose does not appear to be due to a loss of adenosine triphosphate or inorganic orthophosphate. The mutant, however, utilizes glucose-6-phosphate produced intracellularly. Release of carbon dioxide from specifically labeled glucose suggests a C-l preferential cleavage. The kinetics of glucose-6-phosphate accumulation during glucose utilization in the mutant is not consistent with the notion that the utilization of glucose is controlled by glucose-6-phosphate.     

Fructose supports glycogen accumulation,heterocysts differentiation,N2 fixation and growth of the isolated cyanobiont Anabaena azollae

Cells of the cyanobiont Anabaena azollae isolated from the water fern Azolla filiculoides were found to take up and utilize fructose in the light for mixotrophic growth. Fructose was favored by the cyanobiont as a substrate over sucrose and glucose. Cell growth in the presence of 8 mM fructose led to glycogen accumulation in the cells which approached 20% of the cell dry weight within 2 to 3 days, followed by reduction of glycogen content during the fourth day. Glucose-6-phosphate dehydrogenase activity was increased 5–6-fold in the fructose grown cells from the third day of growth onwards. The frequency of heterocysts in fructose-grown cells increased from 6 to 18%, and acetylene reduction by nitrogenase was increased 3-fold in the presence of fructose as compared with control cells, with maximum values observed between the third and fifth day of mixotrophic growth. Fructose-supported growth yielded a 2–4-fold increase in cell dry weight over controls.It is suggested that fructose-supported development and growth of the cyanobiont in batch cultures may resemble its mixotrophic growth and development in situ in the leaf cavity of the host fern Azolla.Abbreviation G6PDH glucose-6-phosphate dehydrogenase     

Insulin action in intact mouse diaphragm I.

Summary The incubation of intact mouse diaphragms with insulin caused a dose and time dependent increase in the independent activity of glycogen synthase in tissue extracts. 2-deoxyglucose (2–10 mm) alone markedly stimulated the conversion of glycogen synthase to the independent activity under conditions in which tissue ATP concentrations were not affected. The incubation of diaphragms with both insulin and 2-deoxyglucose resulted in a greater than additive effect. Insulin stimulated the uptake of 2-deoxyglucose into mouse diaphragms, accumulating as 2-deoxyglucose-6-phosphate. The accumulation of 2-deoxyglucose-6-phosphate correlated well with the increase in the independent activity of glycogen synthase and with the activation of glycogen synthase phosphatase in tissue extracts. The uptake of 3-0-methyl glucose was also markedly stimulated by insulin, without affecting the activity of glycogen synthase. Both glucose-6-phosphate and 2-deoxyglucose-6-phosphate stimulated the activation of endogenous glycogen synthase phosphatase activity in muscle homogenates. We conclude that insulin, in addition to its effects in the absence of exogenous sugars, increases the independent activity of glycogen synthase through increased sugar transport resulting in increased concentrations of sugar-phosphates which promote the activity of glycogen synthase phosphatase.Abbreviations GS Glycogen synthase - GS-I Glycogen synthase activity independent of G6P - GS-D Glycogen synthase activity dependent on G6P - G6P Glucose-6-phosphate - ATP Adenosine triphosphate - EDTA Ethylene diamine tetracetic acid - Mops Morpholinopropane sulfonic acid - 2DG 2-Deoxy glucose - 3-0-MG 3-0-Methyl glucose - tricine N-tris(Hydroxymethyl)methyl glycine Enzymes: Glycogen Synthase — UDPGlucose — Glycogen Glucosyl — Transferase (EC 2.4.1.11) J. Larner is an established investigator of the American Diabetes Association.     

Histochemical studies on glycogen synthetase activity by autoradiographic method

Summary Glycogen synthetase (uridine diphosphate glucose-glycogen glucosyl transferase) was studied in different organs by a histoautoradiographic method and by usual staining methods. This activity was found to be present in muscles and liver of different animals. Human skin also showed some activity. Human liver and myocardium showed the highest activity.In the present study, it was found that the glucose-6-phosphate dependent form (D-form) of the glycogen synthetase predominates over the glucose-6-phosphate independent form (I-form) in all the organs except hamster liver where the I-form predominates.Addition of calcium chloride in the incubation medium, to prevent phosphorolytic breakdown of the newly synthesized glycogen, does not improve the reaction. No glucose is incorporated into glycogen from ¹⁴C-glucose-6-phosphate of the incubation medium for glycogen synthetase. Fixation in absolute alcohol at –20° is recommended for tissues where cytolysis is caused by the incubation medium.     

Inactivation of the phosphoglucomutase gene pgm in Corynebacterium glutamicum affects cell shape and glycogen metabolism

In Corynebacterium glutamicum formation of glc-1-P (α-glucose-1-phosphate) from glc-6-P (glucose-6-phosphate) by α-Pgm (phosphoglucomutase) is supposed to be crucial for synthesis of glycogen and the cell wall precursors trehalose and rhamnose. Furthermore, Pgm is probably necessary for glycogen degradation and maltose utilization as glucan phosphorylases of both pathways form glc-1-P. We here show that C. glutamicum possesses at least two Pgm isoenzymes, the cg2800 (pgm) encoded enzyme contributing most to total Pgm activity. By inactivation of pgm we created C. glutamicum IMpgm showing only about 12% Pgm activity when compared to the parental strain. We characterized both strains during cultivation with either glucose or maltose as substrate and observed that (i) the glc-1-P content in the WT (wild-type) and the mutant remained constant independent of the carbon source used, (ii) the glycogen levels in the pgm mutant were lower during growth on glucose and higher during growth on maltose, and (iii) the morphology of the mutant was altered with maltose as a substrate. We conclude that C. glutamicum employs glycogen as carbon capacitor to perform glc-1-P homeostasis in the exponential growth phase and is therefore able to counteract limited Pgm activity for both anabolic and catabolic metabolic pathways.     

Biosynthesis of Glycogen and Starch in Cryptococcus laurentii

Cells of Cryptococcus laurentii, when grown in liquid culture on 2% glucose close to neutral pH, showed glycogen granules throughout the cytoplasm. Glycogen levels of C. laurentii cells reached maximal levels just before onset of stationary phase. Concomitantly, a sharp rise in total and specific activity of glycogen synthetase was observed. Conversely, glycogen phosphorylase reached its highest specific activity approximately 3 hr after the glycogen peaked and remained high until most of the endogenous glycogen was utilized. Uridine diphosphoglucose pyrophosphorylase activity was always an order of magnitude higher than glycogen synthetase during log phase, but fell off rapidly after the cells reached stationary growth. Kinetic properties of the glycogen synthetase showed that the enzyme is always activated by glucose-6-phosphate, although the degree of activation by glucose-6-phosphate was found to be somewhat variable. The accelerated uptake of glucose commencing with the onset of stationary phase is explained by the rapid formation of extracellular acidic polysaccharide, which continues as long as there is glucose in the medium. In cells grown at pH 3.4, where no detectable extracellular acidic polysaccharide was formed, glucose uptake drastically declined when the cells reached stationary phase. These cells also contained glycogen-like granules in the cytoplasm. The evidence presented indicates that these granules are in fact glycogen, and that its structure does not resemble that of the starch excreted by cells grown at acidic pH.     

An experimental study on carbon flow in Escherichia coli as a function of kinetic properties and expression levels of the enzyme phosphoglucomutase

Mutants of Escherichia coli deficient in phosphoglucomutase accumulate amylose when the cells are grown on maltose or galactose as carbon source. In the presence of physiological levels of phosphoglucomutase, most of the sugar is catabolized, leading to strongly reduced levels of amylose accumulation. By varying the expression level of heterologous phosphoglucomutase, we show that the minimum level needed to block amylose accumulation corresponds to a phosphoglucomutase activity of 150-600 nmole substrate transformed per min per mg of total soluble protein. Mutant phosphoglucomutases with strongly reduced Vmax values and increased Km values for the substrate glucose-1-phosphate or the co-substrate glucose-1,6-diphosphate, could also reduce amylose accumulation, but much higher enzyme expression levels were required.     

Glycogen synthase in prenatal rat liver

Glycogen synthase first appears in significant levels in fetal rat liver on day 18 of gestation (22 day term), but in a mostly inactive, phospho- form. This was reflected in a decreased affinity for its allosteric activator (increased A0.5 for glucose-6-phosphate), and with limited glycogen synthesis and accumulation. Peak glycogen synthesis occurs on day 21 of gestation, and glycogen synthase is in a more dephospho-form with decreased A0.5 for G6P and increased -G6P/+G6P activity ratio. The data suggest that a significant change in phosphorylation state of synthase occurs in late gestation to facilitate the large increase in glycogen synthesis and accumulation.     

Fine structural properties of natural and synthetic glycogens

Glycogen, highly branched (1→4)(1→6)-linked α-d-glucan, can be extracted from natural sources such as animal tissues or shellfish (natural source glycogen, NSG). Glycogen can also be synthesized in vitro from glucose-1-phosphate using the cooperative action of α-glucan phosphorylase (GP, EC 2.4.1.1) and branching enzyme (BE, EC 2.4.1.18), or from short-chain amylose by the cooperative action of BE and amylomaltase (AM, EC 2.4.1.25). It has been shown that enzymatically synthesized glycogen (ESG) has structural and physicochemical properties similar to those of NSG. In this study, the fine structures of ESG and NSG were analyzed using isoamylase and α-amylase. Isoamylase completely hydrolyzed the α-1,6 linkages of ESG and NSG. The unit-chain distribution (distribution of degrees of polymerization (DP) of α-1,4 linked chains) of ESG was slightly narrower than that of NSG. α-Amylase treatment revealed that initial profiles of hydrolyses of ESG and NSG were almost the same: both glycogens were digested slowly, compared with starch. The final products from NSG by α-amylase hydrolysis were glucose, maltose, maltotriose, branched oligosaccharides with DP ? 4, and highly branched macrodextrin molecules with molecular weights of up to 10,000. When ESG was digested with excess amounts of α-amylase, much larger macrodextrins (molecular weight > 10⁶) were detected. In contrast, oligosaccharides with DP 4-7 could not be detected from ESG. These results suggest that the α-1,6 linkages in ESG molecules are more regularly distributed than those in NSG molecules.     

Trehalose and glycogen accumulation is related to the duration of the G1 phase of Saccharomyces cerevisiae

Several factors may control trehalose and glycogen synthesis, like the glucose flux, the growth rate, the intracellular glucose-6-phosphate level and the glucose concentration in the medium. Here, the possible relation of these putative inducers to reserve carbohydrate accumulation was studied under well-defined growth conditions in nitrogen-limited continuous cultures. We showed that the amounts of accumulated trehalose and glycogen were regulated by the growth rate imposed on the culture, whereas other implicated inducers did not exhibit a correlation with reserve carbohydrate accumulation. Trehalose accumulation was induced at a dilution rate (D)相似文献   

Photosystem II regulation of macromolecule synthesis in the blue-green alga Aphanocapsa 6714.

Polymers synthesized by heterotrophically growing (glucose as carbon source) cultures of Aphanocapsa 6714 were compared with polymers synthesized in photosynthetically grown cultures. Loss of photosystem II by dark incubation, or inhibition of light-grown cells with the photosystem II-specific inhibitor dichlorophenylmethylurea, caused an 80 to 90% reduction in the rate of lipid and total ribonucleic acid synthesis, and more than a 90% reduction in the rate of protein synthesis. In contrast, glycogen synthesis was reduced only about 50% in dark cells and less than 30% in dichlorphenylmethylurea-inhibited cells. After longer heterotrophic growth, glycogen became the major component, whereas in photosynthetically grown cultures protein was the major constituent. 14C (from 14CO2 and/or [14C]glucose) assimilated into protein by heterotrophically grown cells was found in amino acids in nearly the same proportions as in photosynthetically grown cells. Thus, routes of biosynthesis available to autotropic cells were also available to heterotrophic cultures, but the supply of carbon precursors to those pathways was greatly reduced. The limited biosynthesis in heterotrophic cells was not due to a limitation for cellular energy. The adenylates were maintained at nearly the same concentrations (and hence the energy charge also) as in photosynthetic cells. The concentration of reduced nicotinamide adenine dinucleotide phosphate was higher in heterotrophic (dark) cells than in photosynthetic cells. From rates of CO2 fixation and/or glycogen biosynthesis it was determined that stationary-phase cells expended approximately 835, 165, and less than 42 nmol of adenosine 5'-triphosphate per mg (dry weight) of algae per 30 min during photosynthetic, photoheterotrophic, and chemoheterotrophic metabolism, respectively. Analysis of the soluble metabolite pools in dark heterotrophic cultures by double-labeling experiments revealed rapid equilibration of 14C through the monophosphate pools, but much slower movement of label into the diphosphate pools of fructose-1,6-diphosphate and sedoheptulose-1,7-diphosphate. Carbon did flow into 3-phosphoglycerate in the dark; however, the initial rate was low and the concentration of this metabolite soon fell to an undetectable level. In photosynthetic cells, 14C quickly equilibrated throughout all the intermediates of the reductive pentose cycle, in particular, into 3-phosphoglycerate. Analysis of glucose-6-phosphate dehydrogenase in cell extracts showed that the enzyme was very sensitive to product inhibition by reduced nicotinamide adenine dinucleotide.     

An automatic enzymatic determination of glycogen in a continuous-flow system without interference of free glucose.

An autoanalyzer system for enzymatic determination of glycogen is described. Free glucose is eliminated by hexokinase/glucose-6-phosphate dehydrogenase. Glycogen is hydrolyzed by amylo-1,6-glycosidase at pH 4,8, and the resulting glucose is dialyzed and determined by the hexokinase/glucose-6-phosphate dehydrogenase reaction.     

Last Step in the Conversion of Trehalose to Glycogen: A MYCOBACTERIAL ENZYME THAT TRANSFERS MALTOSE FROM MALTOSE 1-PHOSPHATE TO GLYCOGEN

We show that Mycobacterium smegmatis has an enzyme catalyzing transfer of maltose from [¹⁴C]maltose 1-phosphate to glycogen. This enzyme was purified 90-fold from crude extracts and characterized. Maltose transfer required addition of an acceptor. Liver, oyster, or mycobacterial glycogens were the best acceptors, whereas amylopectin had good activity, but amylose was a poor acceptor. Maltosaccharides inhibited the transfer of maltose from [¹⁴C]maltose-1-P to glycogen because they were also acceptors of maltose, and they caused production of larger sized radioactive maltosaccharides. When maltotetraose was the acceptor, over 90% of the ¹⁴C-labeled product was maltohexaose, and no radioactivity was in maltopentaose, demonstrating that maltose was transferred intact. Stoichiometry showed that 0.89 μmol of inorganic phosphate was produced for each micromole of maltose transferred to glycogen, and 56% of the added maltose-1-P was transferred to glycogen. This enzyme has been named α1,4-glucan:maltose-1-P maltosyltransferase (GMPMT). Transfer of maltose to glycogen was inhibited by micromolar amounts of inorganic phosphate or arsenate but was only slightly inhibited by millimolar concentrations of glucose-1-P, glucose-6-P, or inorganic pyrophosphate. GMPMT was compared with glycogen phosphorylase (GP). GMPMT catalyzed transfer of [¹⁴C]maltose-1-P, but not [¹⁴C]glucose-1-P, to glycogen, whereas GP transferred radioactivity from glucose-1-P but not maltose-1-P. GMPMT and GP were both inhibited by 1,4-dideoxy-1,4-imino-d-arabinitol, but only GP was inhibited by isofagomine. Because mycobacteria that contain trehalose synthase accumulate large amounts of glycogen when grown in high concentrations of trehalose, we propose that trehalose synthase, maltokinase, and GMPMT represent a new pathway of glycogen synthesis using trehalose as the source of glucose.     

Glycogen metabolism in novikoff ascites-hepatoma cells

A study of the enzymes of the glycogen pathway in Novikoff ascites hepatoma shows that glycogen synthetase has the lowest activity and that the tumour contains no high-K(m) soluble glucokinase. However, incubation of tumour cells with metabolizable sugars in vitro, or intraperitoneal administration of glucose into the tumour-bearing rat, results in glycogen accumulation by the tumour cells. Glycogen synthesis in the tumour is supported by aerobically produced ATP but is decreased anaerobically and by uncouplers of oxidative phosphorylation. Absence of P(i) from the incubation medium increases glycogen synthesis and decreases glycolysis. The optimum temperature for glycogen synthesis is 37 degrees . The capacity of the intact tumour cell to degrade deposited glycogen is low, but is accelerated by 2,4-dinitrophenol. Tumour homogenates prepared after osmotic shock do not incorporate [(14)C]glucose into glycogen. The glucose moiety of glucose 1-phosphate and of UDP-glucose is incorporated into glycogen by the homogenates and the incorporation of glucose 1-phosphate is greatly enhanced by AMP. Glucose 6-phosphate is a poor precursor of glycogen in the homogenate system, probably because it inhibits activation of phosphorylase b by AMP.     

Glycogen and trehalose accumulation during colony development in Streptomyces antibioticus

Streptomyces antibioticus accumulated glycogen and trehalose in a characteristic way during growth on solid medium. Glycogen storage in the substrate mycelium took place during development of the aerial mycelium. The concentration of nitrogen source in the culture medium influenced the time at which accumulation started as well as the maximum levels of polysaccharide stored. Degradation of these glycogen reserves was observed near the beginning of sporulation. The onset of sporogenesis was always accompanied by a new accumulation of glycogen in sporulating hyphae. During spore maturation the accumulated polysaccharide was degraded. No glycogen was observed in aerial non-sporulating hyphae or in mature spores. Trehalose was detected during all phases of colony development. A preferential accumulation was found in aerial hyphae and spores, where it reached levels up to 12% of the cell dry weight. The possible roles of both carbohydrates in the developmental cycle of Streptomyces are discussed.