Carbohydrate Metabolism of the Saccharolytic Alkaliphilic Anaerobes Halonatronum saccharophilum,Amphibacillus fermentum,and Amphibacillus tropicus

The saccharolytic anaerobic bacteria Halonatronum saccharophilum, Amphibacillus fermentum, and Amphibacillus tropicus produce formate, the main fermentation product. In the alkaliphilic community, formate is used as the preferential substrate for sulfate reduction. To reveal the pathways of carbohydrate fermentation by these bacteria, the activity of the key enzymes of carbohydrate metabolism and their pH dependence was studied. It was established that H. saccharophilum utilized glucose by the fructose bisphosphate and hexose monophosphate pathways, and A. tropicus, by the fructose bisphosphate and Entner–Doudoroff pathways. The activity of the key enzymes of all three pathways of glucose metabolism was detected in Amphibacillus fermentum. According to the data obtained, the glucose catabolism in H. saccharophilum, A. fermentum, and A. tropicus mainly proceeds via the fructose bisphosphate pathway. The pH optima of the key enzymes of the glucose metabolism of the alkaliphiles are shifted to alkaline values. In A. tropicus, formate is formed from pyruvate under the action of pyruvate formate-lyase; and in the haloanaerobe H. saccharophilum, formate dehydrogenase is involved in formate metabolism.     

Amphibacillus fermentum sp. nov., Amphibacillus tropicus sp. nov.--new alkaliphilic, facultatively anaerobic, saccharolytic Bacilli from Lake Magadi]

New alkaliphilic, saccharolytic, rod-shaped, gram-positive bacteria resistant to heating and drying and phylogenetically affiliated to the Bacillus lineage were isolated under strictly anaerobic conditions from sediments of the alkaline and highly mineralized Lake Magadi. Strain Z-7792 forms endospores; in strain Z-7984, endospore formation was not revealed. The strains are capable of both anaerobic growth (at the expense of fermentation of glucose and certain mono- and disaccharides with the formation of formate, ethanol, and acetate) and aerobic growth. Among polysaccharides, the strains hydrolyze starch, glycogen, and xylan. Yeast extract or methionine are required for growth. The strains are strict alkaliphiles exhibiting obligate requirement for Na+ and carbonate ions but not for Cl- ion. Growth occurs at a total mineralization as high as 3.3-3.6 M Na+, with an optimum at 1-1.7 M Na+. Strain Z-7792 is an obligate alkaliphile with a pH growth range of 8.5-11.5 and an optimum of 9.5-9.7. Strain Z-7984 grows in a pH range of 7.0-10.5 with an optimum at 8.0-9.5. Both strains are mesophiles having a growth optimum at 37-38 degrees C. They belong to bacilli with a low G + C content. The G + C contents of the DNA of strains Z-7792 and Z-7984 are 39.2 and 41.5 mol%, respectively. These isolates of facultatively anaerobic, strictly alkaliphilic, Na(+)-dependent bacilli can be considered representatives of the ecological group adapted to the life at drying-up shoars of soda lakes. Because of their independence of NaCl and lack of obligate dependence on sodium carbonates, the isolates are to be assigned to athalassophilic organisms. According to their physiological and phylogenetic characteristics, they taxonomically belong to group 1 of the species of bacilli, occupying a position intermediate between the genera Amphibacillus and Gracilibacillus. The isolates are described as new species of Amphibacillus: A. fermentum (type strain, Z-7984T) and A. tropicus (type strain, Z-7792T).     

Multiple and reversible hydrogenases for hydrogen production by Escherichia coli: dependence on fermentation substrate, pH and the F(0)F(1)-ATPase

Molecular hydrogen (H(2)) can be produced via hydrogenases during mixed-acid fermentation by bacteria. Escherichia coli possesses multiple (four) hydrogenases. Hydrogenase 3 (Hyd-3) and probably 4 (Hyd-4) with formate dehydrogenase H (Fdh-H) form two different H(2)-evolving formate hydrogen lyase (FHL) pathways during glucose fermentation. For both FHL forms, the hycB gene coding small subunit of Hyd-3 is required. Formation and activity of FHL also depends on the external pH ([pH](out)) and the presence of formate. FHL is related with the F(0)F(1)-ATPase by supplying reducing equivalents and depending on proton-motive force. Two other hydrogenases, 1 (Hyd-1) and 2 (Hyd-2), are H(2)-oxidizing enzymes during glucose fermentation at neutral and low [pH](out). They operate in a reverse, H(2)-producing mode during glycerol fermentation at neutral [pH](out). Hyd-1 and Hyd-2 activity depends on F(0)F(1). Moreover, Hyd-3 can also work in a reverse mode. Therefore, the operation direction and activity of all Hyd enzymes might determine H(2) production; some metabolic cross-talk between Hyd enzymes is proposed. Manipulating of different Hyd enzymes activity is an effective way to enhance H(2) production by bacteria in biotechnology. Moreover, a novel approach would be the use of glycerol as feedstock in fermentation processes leading to H(2) production, reduced fuels and other chemicals with higher yields than those obtained by common sugars.     

Anaerobic glucose and serine metabolism in Staphylococcus epidermidis

Anaerobically grown Staphylococcus epidermidis fermented glucose with the production of lactate and trace amounts of acetate, formate and CO2. Isotopic and inhibitor studies, assays for key enzymes of different metabolic pathways, and fermentation balances, all indicated that glucose was metabolized principally via glycolysis and to a very limited extent by the hexose monophosphate oxidative pathway. Serine fermentation proceeded via deamination and dismutation yielding NH3 and equimolar amounts of lactate, acetate and CO2; small amounts of formate arose by the operation of pyruvate-formate lyase. Incorporation of 0.5% (w/v) glucose in the growth medium depressed serine metabolism by repressing the activities of serine dehydratase and pyruvate dehydrogenase but, conversely, enhanced the activities of phosphofructokinase and lactate dehydrogenase. Glucose-grown organisms at various stages of anaerobic batch growth showed an inverse relationship between the rates of fermentation of serine and glucose. L-Lactate dehydrogenase activity in crude extracts depended on fructose 1,6-bisphosphate, and fructose 1,6-bisphosphate aldolase was found to be a class I aldolase. Despite the presence of ribokinase, D-ribose-5-phosphate isomerase, transaldolase and transketolase, the organisms utilized ribose only after growth aerobically in basal medium, and then at a slow rate after an initial lag period.     

A comparison of the properties of fructose 1,6-diphosphatase, and the activities of other key enzymes of carbohydrate metabolism, in the livers of embryonic and adult rat, sheep and domestic fowl

1. The activities of some key enzymes of glycolysis and gluconeogenesis were measured in embryonic chick, sheep and rat livers. 2. In chicken the activities of hexokinase, phosphofructokinase and pyruvate kinase are low, but those of glucose 6-phosphatase and fructose diphosphatase are very high; the converse situation exists in the rat (Burch et al. 1963), but in sheep the activities of both phosphofructokinase and fructose diphosphatase are high, and the activities of hexokinase and glucose 6-phosphatase are low. These findings are discussed in relation to carbohydrate metabolism in these embryonic livers. 3. The regulatory properties of fructose diphosphatase from the embryonic livers of these three species were compared with the properties of the enzymes from adult animals. The inhibitions by AMP and fructose diphosphate and the effects of Mg(2+) and pH on the activities of adult and foetal fructose diphosphatase are almost identical. 4. It is concluded that regulatory properties are characteristic of fructose diphosphatase from embryonic and adult tissue, and the importance of this in relation to enzyme development is discussed.     

Proteomics analysis of Bifidobacterium longum NCC2705 growing on glucose, fructose, mannose, xylose, ribose, and galactose

To investigate the molecular mechanisms underlying carbohydrate uptake and connected metabolic pathways of Bifidobacterium longum NCC2705, the proteomic profiles of bacteria grown on different carbon sources including glucose, fructose, mannose, xylose, ribose, and galactose were analyzed. Our results show that all sugars tested were catabolized via the bifid shunt. Sixty-eight proteins that exhibited changes in abundance of threefold or greater were identified by MS. A striking observation was the differential expression of proteins related to the pyruvate metabolism. Further analysis of acetic acid and lactic acid in the culture supernatants by HPLC at the end of fermentation showed that more lactic acid was produced during growth on fructose, ribose, xylose, galactose and more acetic acid was produced during the fermentation of glucose and mannose. Growth experiments revealed that B. longum NCC2705 preferentially used fructose, ribose, xylose, and galactose with higher growth rates over glucose and mannose. Furthermore, five proteins (GroEL, Eno, Tal, Pgm, and BL0033) exhibited clear phosphorylation modifications at serine and/or tyrosine residues. BL0033, a component of an ATP-binding cassette (ABC) transporter, was significantly more abundant in bacteria grown on fructose and, to a lesser extent, ribose and xylose. RT-PCR analysis revealed that all genes of the ABC transporter are induced in the presence of these sugars suggesting that BL0033, BL0034, BL0035, and BL0036 constitute an ABC transporter with fructose as preferred substrate.     

Fermentation of Glucose, Fructose, and Xylose by Clostridium thermoaceticum: Effect of Metals on Growth Yield, Enzymes, and the Synthesis of Acetate from CO2

Clostridium thermoaceticum ferments xylose, fructose, and glucose with acetate as the only product. In fermentations with mixtures of the sugars, xylose is first fermented, then fructose, and last, glucose. Fructose inhibits the fermentation of glucose, and this inhibition appears to be due to a repression of the synthesis of an enzyme needed for glucose utilization. Addition of metals to the culture medium increases the cell yield drastically from about 7 to 18 g per liter, and Y(glucose) values between 40 and 50 are obtained. According to the postulated pathways of the fermentation of glucose and synthesis of acetate from CO(2) by C. thermoaceticum, 3 mol of ATP are available as energy for growth. Thus a Y(adenosine 5'-triphosphate) of 13 to 16 is obtained. Because the normal Y(ATP) value is 10.5, this could mean that an additional source of ATP is available by an unknown mechanism. The addition of metals also increases the nicotinamide adenine dinucleotide phosphate-dependent formate dehydrogenase activity, the overall reaction ((14)CO(2) --> acetate), and the incorporation of the methyl group of 5-methyltetrahydrofolate into acetate. These reactions are catalyzed very efficiently by cells harvested in early growth, whereas cells obtained at the end of a fermentation have very low formate dehydrogenase activity and capacity to incorporate CO(2) into acetate. The following enzymes involved in the synthesis of acetate from CO(2) and in the metabolism of pyruvate are present in extracts of C. thermoaceticum: 10-formyltetrahydrofolate synthetase, 5,10-methenyltetrahydrofolate cyclohydrolase, 5,10-methylenetetrahydrofolate dehydrogenase, 5,10-methylenetetrahydrofolate reductase, phosphate acetyltransferase, and acetate kinase. These enzymes are not or are very little affected by the addition of metals to the growth medium.The amount of corrinoids in cells from early growth is low, whereas it is high in cells harvested late in growth. The opposite is found for the activity of delta-aminolevulinate dehydratase, which is high at the beginning of growth and low at the end.     

Multiple and reversible hydrogenases for hydrogen production by Escherichia coli: dependence on fermentation substrate,pH and the F0F1-ATPase

Molecular hydrogen (H₂) can be produced via hydrogenases during mixed-acid fermentation by bacteria. Escherichia coli possesses multiple (four) hydrogenases. Hydrogenase 3 (Hyd-3) and probably 4 (Hyd-4) with formate dehydrogenase H (Fdh-H) form two different H₂-evolving formate hydrogen lyase (FHL) pathways during glucose fermentation. For both FHL forms, the hycB gene coding small subunit of Hyd-3 is required. Formation and activity of FHL also depends on the external pH ([pH]_out) and the presence of formate. FHL is related with the F₀F₁-ATPase by supplying reducing equivalents and depending on proton-motive force. Two other hydrogenases, 1 (Hyd-1) and 2 (Hyd-2), are H₂-oxidizing enzymes during glucose fermentation at neutral and low [pH]_out. They operate in a reverse, H₂-producing mode during glycerol fermentation at neutral [pH]_out. Hyd-1 and Hyd-2 activity depends on F₀F₁. Moreover, Hyd-3 can also work in a reverse mode. Therefore, the operation direction and activity of all Hyd enzymes might determine H₂ production; some metabolic cross-talk between Hyd enzymes is proposed. Manipulating of different Hyd enzymes activity is an effective way to enhance H₂ production by bacteria in biotechnology. Moreover, a novel approach would be the use of glycerol as feedstock in fermentation processes leading to H₂ production, reduced fuels and other chemicals with higher yields than those obtained by common sugars.     

Characteristics of carbohydrate metabolism of R-, S- i M-dissociants of Pseudomonas aeruginosa]

R and S dissociants of the hydrocarbon-oxidizing strain Pseudomonas aeruginosa K-2 differed but little in their growth in a minimal defined medium with glucose as the source of carbon and energy. At the same time, the number of cells of M dissociant in the late exponential phase was five orders of magnitude less than that of R and S dissociants. The growth of M dissociant was accompanied by the accumulation of formate in the culture liquid and a concurrent decrease in pH. All three dissociants contained the key enzymes of the Entner-Doudoroff pathway of glucose oxidation; however, the activities of these enzymes, especially 6-phosphogluconate dehydrogenase, were low in M dissociant. Conversely, the activity of formate dehydrogenase in cells of M dissociant was higher than in other dissociants. The activity of 6-phosphogluconate dehydrogenase, a key enzyme of the pentosephosphate pathway of glucose oxidation, was detected only in S dissociant. The peculiarities of the carbohydrate metabolism of M dissociant are probably responsible for its poor growth on glucose and determine the more pronounced anaerobic type of its metabolism.     

Comparative study of the energy metabolism of anaerobic alkaliphiles from soda lakes

We investigated the influence of inhibitors of energy metabolism and ionophores on the growth and formation of metabolic products in alkaliphilic anaerobes characterized by various catabolism types. It was shown that blockage of oxidative phosphorylation by the addition of N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of F1F0 ATP synthase, resulted in a complete arrest of the growth of the acetogenic bacterium Tindallia magadiensis with arginine as electron acceptor. In the presence of pyruvate, substrate-level phosphorylation occurred. The methylotrophic methanogenic archaebacterium Methanosalus zhilinae did not grow with DCCD and vanadate, an inhibitor of E1E2 ATPase, suggesting the presence of two ATPase types in this species. In the saccharolytic alkaliphiles Halonatronum, Amphibacillus tropicus, and Spirochaeta alkalica (which are characterized by different pH optima), the contribution of the H+ gradient to the energy metabolism and, presumably, to the maintenance of the intracellular pH level decreased with an increase in the degree of alkaliphily. Based on the data of an inhibitor assay using protonophores, monensin, and amiloride, we suggest that all of the bacteria tested depend on H+- and Na+-gradients. The Na+/H+ antiport appears to be a universal mechanism of regulating the intracellular pH level and the interaction between the Na+ and the H+ cycles in bacterial cells cultivated under alkaline conditions.     

The physiology of Lactococcus lactis subsp. lactis biovar. diacetylactis immobilized in hollow-fibre bioreactors: glucose,lactose and citrate metabolism at high cell densities

Lactococcus lactis subsp. lactis biovar. diacetylactis was selected to study the physiological influences of immobilization and growth to high cell densities. Cells were cultivated on glucose or lactose medium in the presence and absence of citrate. With excess glucose the cells produced mainly lactate as the fermentation product (homofermentative) providing that not all of the substrate was consumed. The population so cultivated was exposed to extreme gradients of pH and lactate concentrations. When the glucose concentration was reduced the population showed a mixed product profile with half of the glucose being fermented to lactate, the remainder to formate, acetate, ethanol and 2,3-butanediol. Inclusion of citrate in the medium shifted the population to homofermentation, with respect to the amount of glucose or lactose consumed. The citrate was metabolized via the pyruvate-formate lyase and -acetolactate synthase routes. The pH of the medium was shown to strongly influence the product profile from citrate, presumably by affecting the activity of the key enzymes of pyruvate metabolism. The lactococci immobilized at high cell densities show product profiles typical of carbohydrate limitation at low dilution rates. Correspondence to: M. R. Smith     

Effect of dilution rate and carbon availability on Bifidobacterium breve fermentation

Bifidobacterium breve NCFB 2257 was grown in glucose-limited and nitrogen (N)-limited chemostats at dilution rates (D) from 0.04 to 0.60 h^–1, to study the effect of nutrient availability on carbohydrate metabolism. The results showed that D had little effect on fermentation product formation, irrespective of the form of nutrient limitation. However, marked differeces were observed in the distribution of fermentation products, that were attributable to glucose availability. In glucose-limited cultures, formate and acetate were the principal end-products of metabolism. Lactate was never detected under these growth conditions. In contrast, lactate and acetate were mainly formed when glucose was in excess, and formate was not produced. These results are explained by the metabolic fate of pyruvate, which can be dissimilated by either phosphoroclastic cleavage to acetyl phosphate and formate, or alternatively, it may be reduced to lactate. Enzymic studies were made to establish the mechanisms that regulated pyruvate metabolism. The data demonstrated that control was not exercised through regulation of the synthesis and activity of lactate dehydrogenase (LDH), phosphofructokinase or alcohol dehydrogenase. It is possible however, that there was competition for pyruvate by LDH and the phosphoroclastic enzyme, which would determine the levels of lactate and formate produced respectively. These results demonstrate the metabolic flexibility of B. breve, which preferentially uses lactate as an electron sink during N-limited growth, whereas under energy-limitation, carbon flow is directed towards acetyl phosphate to maximise ATP synthesis. Correspondence to: B. A. Degnan     

Starch fermentation via a formate producing pathway in Chlamydomonas reinhardii, Chlorogonium elongatum and Chlorella fusca

Starch degradation was investigated during anaerobic dark incubation in the algae Chlamydomonas reinhardii, Chlorogonium elongatum and Chlorella fusca . The pathway of algal formate fermentation was elucidated by determination of the relationship between substrate consumption and product accumulation. The fate of reducing equivalents was also determined. Investigations were done on dependence of pH, fermentation time, cell cycle, and after addition of H₂, hypophosphite and inhibitors of protein synthesis.
A mixed acid fermentation that produced formate, acetate and ethanol (2:1:1) with only small amounts of H₂ and CO₂ was shown for the algal strains used. The failure of inhibition with cycloheximide and chloramphenicol indicated the constitutive presence of all fermenting enzymes. Nevertheless, glycerol, D(–)lactate and stoichiometrical amounts of ethanol and CO₂ were found additionally at extreme pH (pH 4.6 and 7.9), and after addition of H₂ and hypophosphite (7 m M ). During long-term incubation (28 h) fermentation changed from mixed acid to ethanol production. The pathways of algal fermentation did not depend on cell cycle, and fermentation rate corresponded directly to the actual starch content of algal cells. The results gave evidence for synthesis of formate during anaerobic metabolism in algae by a thioclastic cleavage of pyruvate via the enzyme pyruvate formate lyase. This indicated an algal fermentation pathway thought to be present only in procaryotic organisms.     

Effect of <Emphasis Type="Italic">poxB</Emphasis> gene knockout on metabolism in <Emphasis Type="Italic">Escherichia coli</Emphasis> based on growth characteristics and enzyme activities

The effect of poxB gene knockout on metabolism in Escherichia coli was investigated in the present paper based on the growth characteristics and the activities of the enzymes involved in the central metabolic pathways. The absence of pyruvate oxidase reduced the glucose uptake rate and cell growth rate, and increased O₂ consumption and CO₂ evolution. The enzyme assay results showed that although glucokinase activity increased, the flux through glycolysis was reduced due to the down-regulation of the other glycolytic enzymes such as 6-phosphofructosekinase and fructose bisphosphate aldolase in the poxB mutant. TCA cycle enzymes such as citrate synthase and malate dehydrogenase were repressed in the poxB mutant when the cells were cultivated in LB medium. The pyruvate oxidase mutation also resulted in the activation of glucose-6-phosphate dehydrogenase and acetyl-CoA synthetase. All these results suggest that pyruvate oxidase is not only a stationary-phase enzyme as previously known, and that the removal of the poxB gene affects the central metabolism at the enzyme level in E. coli.     

Fluoride, hydrogen, and formate activate ribulosebisphosphate carboxylase formation in Alcaligenes eutrophus

Alcaligenes eutrophus formed ribulosebisphosphate carboxylase (RuBPCase; EC 4.1.1.39) when grown on fructose. Addition of sodium fluoride (NaF) to fructose minimal medium resulted in a slightly decreased growth rate and a rapid fivefold increase in RuBPCase specific activity. With citrate, a glucogenic carbon source, RuBPCase was also formed, However, addition of NaF to cells growing on citrate resulted in a 50% decrease in RuBPCase specific activity. Among the enzymes of fructose catabolism, NaF (10 mM) inhibited enolase in vitro by 98% and gluconate 6-phosphate dehydratase by 87%. Inhibition of the dehydratase by NaF was insignificant in vivo, as determined with a mutant defective in phosphoglycerate mutase activity. Growth of this mutant on fructose was not inhibited by NaF, and only a minor increase in RuBPCase activity was observed. From these results, we concluded that the product of the enolase reaction, phosphoenolpyruvate, played a role in RuBPCase formation. Addition of H2 or formate to the wild type growing on fructose or citrate did not affect the growth rate but resulted in rapid formation of RuBPCase activity. Mutants impaired in H2 metabolism formed RuBPCase at a low rate during growth on fructose plus H2 but at a high rate on formate. Apparently, additional reductant from H2 or formate metabolism induced RuBPCase formation in A. eutrophus.     

利用代谢工程构建D-甘露醇生产菌株

D-甘露醇广泛应用于食品、制药、化学品工业等领域。从野生型大肠杆菌出发,将来自假肠膜明串珠菌Leuconostoc pseudomesenteroides ATCC 12291菌株的甘露醇脱氢酶与果糖转运蛋白编码基因整合到大肠杆菌ATCC 8739的染色体中,并失活其他的发酵途径 (丙酮酸甲酸裂解酶、乳酸脱氢酶、富马酸还原酶、乙醇脱氢酶、甲基乙二醛合成酶和丙酮酸氧化酶) ,构建了一株遗传稳定的D-甘露醇生产菌株。使用无机盐培养基和葡萄糖果糖作为混合碳源,厌氧发酵6 d,D-甘露醇产量达1.2 mmol/L。基于细胞生长和D-甘露醇合成的偶联,进一步通过代谢进化技术提高细胞合成D-甘露醇的生产能力。经过80代的驯化,D-甘露醇产量提高了2.6倍,甘露醇脱氢酶的活性提高了2.8倍。构建获得的遗传稳定的工程菌能直接发酵糖生产D-甘露醇,不需添加抗生素、诱导剂和甲酸,在工业化生产时有一定优势。     

Exopolysaccharide production and peculiarities of C6-metabolism in Acinetobacter sp. grown on carbohydrate substrates

An Acinetobacter sp. strain grown on carbohydrate substrates (mono- and disaccharides, molasses, starch) was shown to synthesize exopolysaccharides (EPS). Glucose catabolism proved to proceed via the Embden-Meyerhof-Parnas and Entner-Doudoroff pathways. Pyruvate entered the tricarboxylic acid cycle due to pyruvate dehydrogenase activity. Pyruvate carboxylation by pyruvate carboxylase was the anaplerotic reaction providing for the synthesis of intermediates for the constructive metabolism of Acinetobacter sp. grown on C6-substrates. The C6-metabolism in Acinetobacter sp. was limited by coenzyme A. Irrespective of the carbohydrate growth substrate (glucose, ethanol), the activities of the key enzymes of both C2- and C6-metabolism was high, except for the isocitrate lyase activity in glucose-grown bacteria. Isocitrate lyase activity was induced by C2-compounds (ethanol or acetate). After their addition to glucose-containing medium, both substrates were utilized simultaneously, and an increase was observed in the EPS synthesis, as well as in the EPS yield relative to biomass. The mechanisms responsible for enhancing the EPS synthesis in Acinetobacter sp. grown on a mixture of C2- and C6-substrates are discussed.     

Assessment of the fructanolytic activities in the rumen bacterium Treponema saccharophilum strain S

AIMS: To characterize the fructose polymer degrading enzymes of rumen bacterium Treponema saccharophilum strain S. METHODS AND RESULTS: Conventional methods were used to examine bacterial growth and enzyme activities. Electrophoretic zymogram under native conditions, and thin layer chromatography, were applied to identify and characterize the enzymes. Treponema saccharophilum utilized Timothy grass fructan, inulin and sucrose but not free fructose. Timothy grass fructan was degraded at a significantly higher rate than sucrose and inulin. Two fructanolytic enzymes were found in the soluble, and one in the membrane fraction of bacterial cell extract. The first degraded each mentioned carbohydrate to monosaccharides. The second released oligosaccharides only from Timothy grass fructan. CONCLUSIONS: The bacterium T. saccharophilum strain S is capable of synthesizing non-specific beta-fructofuranosidases and 2,6-beta-D-fructan fructanohydrolase. The enzymes are of constitutive character. SIGNIFICANCE AND IMPACT OF THE STUDY: It has been stated for the first time that the 2,6-beta-D-fructan fructanohydrolase is synthesized by the rumen bacterium T. saccharophilum. This organism appears to be responsible for grass fructan degradation in the rumen.     

Metabolic adaptation of the renal carbohydrate metabolism. II

Summary The effects of a high carbohydrate diet on the renal gluconeogenic and glycolytic capacities and on the activities of the main enzymes of the carbohydrate metabolism, fructose 1,6-bisphosphatase, phosphofructokinase and pyruvate kinase have been studied. These parameters have been analysed in two separate and isolated fractions of the renal tubule, the proximal convoluted (PCT) and the distal convoluted (DCT) zones. The results presented in this study show a rapid adaptation capacity of the kidney in response to the high amount of dietary carbohydrate, which are characterized by a decrease in the glucose production and fructose 1,6-bisphosphatase activity in the proximal tubules, and an increase in the glycolytic flux and phosphofructokinase and pyruvate kinase activities in the distal tubules. The changes in these enzyme activities took place only at subsaturating substrate concentrations and not at maximum velocity which suggest that they are probably due to an allosteric and/or covalent modifications and so, they are independent of variations in the cellular levels of the enzymes.     

The activity of the carbon metabolism enzymes in Chromatium minutissimum after long-term preservation

The activity of the enzymes of the tricarboxylic acid cycle and glyoxylate shunt, as well as of some enzymes involved in carbohydrate metabolism, were determined in the purple sulfur bacterium Chromatium minutissimum, either maintained by subculturing in liquid medium or stored in the lyophilized state for 36 years. In cultures stored in the lyophilized state, the activities of the key enzymes of the tricarboxylic acid cycle, glyoxylate shunt, and Embden-Meyerhof-Parnas pathway were higher, whereas the activities of glucose-6-phosphate dehydrogenase, pyruvate kinase, and ribulose bisphosphate carboxylase were somewhat lower than in cultures maintained by regular transfers.