Dissimilation of citric acid byStreptococcus paracitrovorus

Summary and conclusions S.paracitrovorus does not readily dissimilate citric acid in the absence of sugar but does attack citric acid relatively vigorously in the presence of small quantities of glucose or lactose. The effect of glucose and lactose in initiating the dissimilation of citric acid is catalytic.The sugars which act catalytically are themselves fermented to approximately equimolar quantities of carbon dioxide, ethyl alcohol and lactic acid. The dissimilation of a combined substrate of citrate and glucose forms, in addition, acetic acid, acetylmethylcarbinol, 2,3-butylene glycol and under certain conditions, pyruvic acid which acts as an intermediate compound. Pyruvate is dissimilated to products similar to those from a fermentation of citrate plus glucose.The reactions ofKrebs' citric acid cycle apparently do not apply to the dissimilation of citric acid byS.paracitrovorus because the fermentation of citric acid proceeds anaerobically, consumes little oxygen aerobically and is not inhibited by arsenite.Inasmuch as milk contains lactose, the fermentation of citric acid in milk byS.paracitrovorus may be catalyzed as shown in these studies.Journal paper No.J711 of the Iowa Agricultural Experiment Station, Project 451.     

Carboligatic activity of escherichia coli

Summary The formation of acetylmethylcarbinol from glucose by Esch. coli in vigorously aerated media constitutes additional proof of the intermediate formation of acetaldehyde in that fermentation. Interference of an accessory hydrogen acceptor (oxygen) preventing immediate reduction of the aldehyde results in its accumulation and condensation. Esch. coli in common with many other organisms possesses the carboligase system.In the presence of glucose, Esch. coli can reduce small quantities of acetylmethylcarbinol to 2,3-butylene glycol.Supported by Industrial Science Research funds of Iowa State College.     

Amino acid metabolism and protein synthesis in a pyrithiamine-requiring Staphylococcus aureus mutant

1. As a result of the mutation of Staphylococcus aureus by pyrithiamine, deletion of the enzyme thiaminokinase in the system occurs. Some properties of thiaminokinase including the effects of pH, pyrophosphate donor nucleotides and metal ions on the enzyme in the parent S. aureus have been studied. Cell-free extract from mutant strain has been studied under similar conditions and thiaminokinase activity was found to be absent. Addition of thiamine (10mug./ml.) to the medium containing pyrithiamine (required for the growth of the mutant strain) did not give rise to thiaminokinase activity in the mutant bacteria. 2. The parent and the mutant strains of S. aureus have been studied for the fermentative production of acetylmethylcarbinol (3-hydroxybutan-2-one) and the mutant strain did not produce acetylmethylcarbinol under the conditions used.     

Thiaminokinase in parent and pyrithiamine mutant Staphylococcus aureus

1. As a result of the mutation of Staphylococcus aureus by pyrithiamine, deletion of the enzyme thiaminokinase in the system occurs. Some properties of thiaminokinase including the effects of pH, pyrophosphate donor nucleotides and metal ions on the enzyme in the parent S. aureus have been studied. Cell-free extract from mutant strain has been studied under similar conditions and thiaminokinase activity was found to be absent. Addition of thiamine (10μg./ml.) to the medium containing pyrithiamine (required for the growth of the mutant strain) did not give rise to thiaminokinase activity in the mutant bacteria. 2. The parent and the mutant strains of S. aureus have been studied for the fermentative production of acetylmethylcarbinol (3-hydroxybutan-2-one) and the mutant strain did not produce acetylmethylcarbinol under the conditions used.     

Substrate Effect on 2,3-Butylene Glycol Production by Rhizopus nigricans and Penicillium expansum

Rhizopus nigricans and Penicillium expansum produced 2,3-butylene glycol which accumulated in natural and artificial media with time. Mycelial mats of P. expansum decreased the quantity of a diacetyl substrate and converted part of this substrate into acetylmethylcarbinol (AMC) and 2,3-butylene glycol. Mycelial mats of P. expansum also decreased AMC substrate with the formation of 2,3-butylene glycol. 2,3-Butylene glycol decreased slightly during incubation with the fungal mat. The formation of AMC was suppressed significantly by cysteine and ascorbic acid.     

Aerobic Metabolism of Streptococcus agalactiae

Streptococcus agalactiae cultures possess an aerobic pathway for glucose oxidation that is strongly inhibited by cyanide. The products of glucose oxidation by aerobically grown cells of S. agalactiae 50 are lactic and acetic acids, acetylmethylcarbinol, and carbon dioxide. Glucose degradation products by aerobically grown cells, as percentage of glucose carbon, were 52 to 61% lactic acid, 20 to 23% acetic acid, 5.5 to 6.5% acetylmethylcarbinol, and 14 to 16% carbon dioxide. There was no evidence for a pentose cycle or a tricarboxylic acid cycle. Crude cell-free extracts of S. agalactiae 50 possessed a strong reduced nicotinamide adenine dinucleotide (NADH(2)) oxidase that is also cyanide-sensitive. Dialysis or ultrafiltration of the crude, cell-free extract resulted in loss of NADH(2) oxidase activity. Oxidase activity was restored to the inactive extract by addition of the ultrafiltrate or by addition of menadione or K(3)Fe(CN)(6). Noncytochrome iron-containing pigments were present in cell-free extracts of S. agalactiae. The possible participation of these pigments in the respiration of S. agalactiae is presently being studied.     

营养条件对光滑球拟酵母发酵生产丙酮酸的影响

丙酮酸是多种氨基酸、维生素及其它有用物质的重要前体,广泛应用于化工、制药及农用化学品工业。能够直接发酵生产丙酮酸的菌种主要有Ａｃｉｎｅｔｏｂａｃｔｅｒ[1],Ｅｎｔｅｒｏｂａｃｔｅｒ[2],Ｅｎｔｅｒｏｃｏｃｃｕｓ[3],Ｅｓｃｈｅｒｉｃｈｉａ[4],Ａｇａｒｉｃｕ?..     

Biological characterization of Bacillus flexus strain SSAI1 transforming highly toxic arsenite to less toxic arsenate mediated by periplasmic arsenite oxidase enzyme encoded by aioAB genes

Bacillus flexus strain SSAI1 isolated from agro-industry waste, Tuem, Goa, India displayed high arsenite resistance as minimal inhibitory concentration was 25 mM in mineral salts medium. This bacterial strain exposed to 10 mM arsenite demonstrated rapid arsenite oxidation and internalization of 7 mM arsenate within 24 h. The Fourier transformed infrared (FTIR) spectroscopy of cells exposed to arsenite revealed important functional groups on the cell surface interacting with arsenite. Furthermore, scanning electron microscopy combined with electron dispersive X-ray spectroscopy (SEM-EDAX) of cells exposed to arsenite revealed clumping of cells with no surface adsorption of arsenite. Transmission electron microscopy coupled with electron dispersive X-ray spectroscopic (TEM-EDAX) analysis of arsenite exposed cells clearly demonstrated ultra-structural changes and intracellular accumulation of arsenic. Whole-genome sequence analysis of this bacterial strain interestingly revealed the presence of large number of metal(loid) resistance genes, including aioAB genes encoding arsenite oxidase responsible for the oxidation of highly toxic arsenite to less toxic arsenate. Enzyme assay further confirmed that arsenite oxidase is a periplasmic enzyme. The genome of strain SSAI1 also carried glpF, aioS and aioE genes conferring resistance to arsenite. Therefore, multi-metal(loid) resistant arsenite oxidizing Bacillus flexus strain SSAI1 has potential to bioremediate arsenite contaminated environmental sites and is the first report of its kind.

     

Arsenite oxidation by the heterotroph Hydrogenophaga sp. str. NT-14: the arsenite oxidase and its physiological electron acceptor

Heterotrophic arsenite oxidation by Hydrogenophaga sp. str. NT-14 is coupled to the reduction of oxygen and appears to yield energy for growth. Purification and partial characterization of the arsenite oxidase revealed that it (1). contains two heterologous subunits, AroA (86 kDa) and AroB (16 kDa), (2). has a native molecular mass of 306 kDa suggesting an alpha(3)beta(3) configuration, and (3). contains molybdenum and iron as cofactors. Although the Hydrogenophaga sp. str. NT-14 arsenite oxidase shares similarities to the arsenite oxidases purified from NT-26 and Alcaligenes faecalis, it differs with respect to activity and overall conformation. A c-551-type cytochrome was purified from Hydrogenophaga sp. str. NT-14 and appears to be the physiological electron acceptor for the arsenite oxidase. The cytochrome can also accept electrons from the purified NT-26 arsenite oxidase. A hypothetical electron transport chain for heterotrophic arsenite oxidation is proposed.     

THE BREAKDOWN OF GLUCOSE BY BACILLUS GLYCOLLACTICUS AND THE EFFECT OF AERATION ON FERMENTATION

SUMMARY: In the decomposition of glucose by Bacillus glycollacticus , CO₂, 2:3-butylene glycol, lactic and acetic acids, ethanol and traces of acetylmethylcarbinol were formed. A satisfactory carbon balance was obtained. Aeration played an important rôle affecting the amounts of products formed and the duration of fermentation. The largest yield of 2:3-butylene glycol obtained was 32.5 mM from 50 mM of glucose.     

Structure of Cyl-2, a Novel Cyclotetrapeptide from Cylindrocladium scoparium

Fermentative production of pyruvic acid by yeasts was studied using extracts from citrus natsudaidai peel as a carbon source. Many yeasts showed good growth. Of these yeasts, Debaryomyces coudertii IFO 1381 produced pyruvic acid at high yield. Pretreatment of the peel extract with Amberlite IR-120B (Na⁺) led to increased production of pyruvic acid. Under optimum conditions, the accumulation of pyruvic acid reached a maximum of 970 mg/100ml at 48 hr-fermentation. The pyruvic acid from the fermentation broth was identified with lactic acid dehydrogenase and by comparisons of properties of its 2,4-dinitrophenylhydrazone with those of authentic pyruvic acid in paper chromatography, IR spectrometry and elemental analysis.     

Molybdenum-containing arsenite oxidase of the chemolithoautotrophic arsenite oxidizer NT-26

The chemolithoautotroph NT-26 oxidizes arsenite to arsenate by using a periplasmic arsenite oxidase. Purification and preliminary characterization of the enzyme revealed that it (i) contains two heterologous subunits, AroA (98 kDa) and AroB (14 kDa); (ii) has a native molecular mass of 219 kDa, suggesting an alpha2beta2 configuration; and (iii) contains two molybdenum and 9 or 10 iron atoms per alpha2beta2 unit. The genes that encode the enzyme have been cloned and sequenced. Sequence analyses revealed similarities to the arsenite oxidase of Alcaligenes faecalis, the putative arsenite oxidase of the beta-proteobacterium ULPAs1, and putative proteins of Aeropyrum pernix, Sulfolobus tokodaii, and Chloroflexus aurantiacus. Interestingly, the AroA subunit was found to be similar to the molybdenum-containing subunits of enzymes in the dimethyl sulfoxide reductase family, whereas the AroB subunit was found to be similar to the Rieske iron-sulfur proteins of cytochrome bc1 and b6f complexes. The NT-26 arsenite oxidase is probably exported to the periplasm via the Tat secretory pathway, with the AroB leader sequence used for export. Confirmation that NT-26 obtains energy from the oxidation of arsenite was obtained, as an aroA mutant was unable to grow chemolithoautotrophically with arsenite. This mutant could grow heterotrophically in the presence of arsenite; however, the arsenite was not oxidized to arsenate.     

Arsenite stimulates plasma membrane NADPH oxidase in vascular endothelial cells

Low-level arsenite treatment of porcine aortic endothelial cells (PAEC) stimulated superoxide accumulation that was attenuated by inhibitors of NAD(P)H oxidase. To demonstrate whether arsenite stimulated NADPH oxidase, intact PAEC were treated with arsenite for up to 2 h and membrane fractions were prepared to measure NADPH oxidase activity. Arsenite (5 microM) stimulated a twofold increase in activity by 1 h, which was inhibited by the oxidase inhibitor diphenyleneiodonium chloride. Direct treatment of isolated membranes with arsenite had no effect. Analysis of NADPH oxidase components revealed that p67(phox) localized exclusively to membranes of both control and treated cells. In contrast, cytosolic Rac1 translocated to the membrane fractions of cells treated with arsenite or angiotensin II but not with tumor necrosis factor. Immunodepletion of p67(phox) blocked oxidase activity stimulated by all three compounds. However, depleting Rac1 inhibited responses only to arsenite and angiotensin II. These data demonstrate that stimulus-specific activation of NADPH oxidase in endothelial cells was the source of reactive oxygen in endothelial cells after noncytotoxic arsenite exposure.     

Arsenic induced progesterone production in a caspase-3-dependent manner and changed redox status in preovulatory granulosa cells

Arsenic contamination is a principal environmental health threat throughout the world. However, little is known about the effect of arsenic on steroidogenesis in granulosa cells (GCs). We found that the treatment of preovulatory GCs with arsenite stimulated progesterone production. A significant increase in serum level of progesterone was observed in female Sprague-Dawley rats following arsenite treatment at a dose of 10 mg/L/rat/day for 7 days. Further experiments demonstrated that arsenite treatment did not change the level of intracellular cyclic AMP (cAMP) or phosphorylated ERK1/2 in preovulatory GCs; however, progesterone production was significantly decreased when cAMP-dependent protein kinase (PKA) or ERK1/2 pathway was inhibited. This implied that the effect of arsenite on progesterone production may require cAMP/PKA and ERK1/2 signaling but not depend on them. Furthermore, we found that arsenite decreased intracellular reactive oxygen species (ROS) but increased the antioxidant glutathione (GSH) levels and mitochondrial membrane potential (ΔΨm) in parallel to the changes in progesterone production. Progesterone antagonist blocked the arsenic-stimulated increase of GSH levels. Arsenite treatment induced caspase-3 activation, although no apoptosis was observed. Inhibition of caspase-3 activity significantly decreased progesterone production stimulated by arsenite or follicle-stimulating hormone (FSH). GSH depletion with buthionine sulfoximine led to cell apoptosis in response to arsenite treatment. Collectively, this study demonstrated for the first time that arsenite stimulates progesterone production through cleaved/active caspase-3-dependent pathway, and the increase of GSH level promoted by progesterone production may protect GCs against apoptosis and maintain the steroidogenesis of GCs in response to arsenite treatment.     

Reverse reaction of malic enzyme for HCO3- fixation into pyruvic acid to synthesize L-malic acid with enzymatic coenzyme regeneration

Malic enzyme [L-malate: NAD(P)(+) oxidoreductase (EC 1.1.1.39)] catalyzes the oxidative decarboxylation of L-malic acid to produce pyruvic acid using the oxidized form of NAD(P) (NAD(P)(+)). We used a reverse reaction of the malic enzyme of Pseudomonas diminuta IFO 13182 for HCO(3)(-) fixation into pyruvic acid to produce L-malic acid with coenzyme (NADH) generation. Glucose-6-phosphate dehydrogenase (EC1.1.1.49) of Leuconostoc mesenteroides was suitable for coenzyme regeneration. Optimum conditions for the carboxylation of pyruvic acid were examined, including pyruvic acid, NAD(+), and both malic enzyme and glucose-6-phosphate dehydrogenase concentrations. Under optimal conditions, the ratio of HCO(3)(-) and pyruvic acid to malic acid was about 38% after 24 h of incubation at 30 degrees C, and the concentration of the accumulated L-malic acid in the reaction mixture was 38 mM. The malic enzyme reverse reaction was also carried out by the conjugated redox enzyme reaction with water-soluble polymer-bound NAD(+).     

Sodium arsenite enhances the cytotoxicity, clastogenicity, and 6-thioguanine-resistant mutagenicity of ultraviolet light in Chinese hamster ovary cells

Cytotoxicity, chromosome aberrations, and mutations to 6-thioguanine resistance were synergistically increased by incubating the ultraviolet light (UV)-irradiated Chinese hamster ovary (CHO) cells in medium containing sodium arsenite. However, the frequencies of sister-chromatid exchanges and mutations to ouabain resistance induced by UV were not synergistically increased by sodium arsenite. The synergistic effect of sodium arsenite on UV-induced chromosome aberrations varied with cell-harvesting time and decreased with increasing time intervals between UV and sodium arsenite treatments.     

Survey of Selected Filamentous Fungi for Voges-Proskauer Reactions

Of 16 filamentous fungi surveyed for Voges-Proskauer reactants, 81.2% were found to be positive. The total group fell into three classes: those producing considerable acetylmethylcarbinol (AMC), those producing a small amount, and those producing no AMC. Oidium lactis had a highly significant effect upon lowering the amount of Voges-Proskauer reactants produced by Rhizopus nigricans.     

Arsenite inhibits Ras-dependent activation of ERK but activates ERK in the presence of oncogenic Ras in baboon vascular smooth muscle cells

Exposure to arsenical compounds enhances the risk of atherosclerosis. The reason is unknown but it might be because an effect of arsenite (As3+) on plaque smooth muscle cells (SMCs) activation of extracellular signal-regulated kinase (ERK), a crucial mediator of SMC function. We found that arsenite inhibits the activation of ERK by platelet-derived growth factor-BB (PDGF-BB). This inhibitory effect depends on the time of arsenite exposure, is reversible, and is attenuated by preincubation of SMCs with the antioxidant N-acetyl-cysteine. These observations are consistent with the assumption that oxidative stress is involved. The blockade of ERK by arsenite may be mediated by an inhibition of Ras as arsenite prevents GTP-loading of Ras in response to PDGF-BB. Moreover, the Ras blockade by arsenite is not specific for PDGF-BB because it was also observed following stimulation of SMCs with EGF. To address the role of Ras, we expressed constitutively active, GTP-bound Ha-Ras (V12Ras). Unexpectedly, in V12Ras expressing-SMCs, arsenite stimulates ERK, but still decreases ERK activity in the presence of PDGF-BB. Our data suggest that arsenite inhibits the Ras/ERK pathway in SMCs, and that arsenite may activate ERK in Ras-transformed cells by mechanisms different from those employed by growth factors.     

Inhibition of repair of radiation-induced DNA double-strand breaks by nickel and arsenite

The effect of arsenite or nickel on the repair of DNA double-strand breaks (DSBs) was studied in gamma-irradiated Chinese hamster ovary cells using pulsed-field gel electrophoresis. After treatment with nickel chloride or arsenite for 2 h, cells were irradiated with gamma rays at a dose of 40 Gy, and the numbers of DNA DSBs were measured immediately after irradiation as well as at 30 min postirradiation. Both arsenite and nickel(II) inhibited repair of DNA DSBs in a concentration-dependent manner; 0.08 mM arsenite significantly inhibited the rejoining of DSBs, while 76 mM nickel was necessary to observe a clear inhibition. The mean lethal concentrations for the arsenite and nickel(II) treatments were approximately 0.12 and 13 mM, respectively. This indicates that the inhibition of repair by arsenite occurred at a concentration at which appreciable cell survival occurred, but that nickel(II) inhibited repair only at cytotoxic concentrations at which the cells lost their proliferative ability. These novel observations provide insight into the mechanisms underlying the effects of combined exposure to arsenite and ionizing radiation in our environment.