Sulfurospirillum barnesii sp. nov. and Sulfurospirillum arsenophilum sp. nov., new members of the Sulfurospirillum clade of the epsilon Proteobacteria.
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Two strains of dissimilatory arsenate-reducing vibrio-shaped bacteria are assigned to the genus Sulfurospirillum. These two new species, Sulfurospirillum barnesii strain SES-3T and Sulfurospirillum arsenophilum strain MIT-13T, in addition to Sulfurospirillum sp. SM-5, two strains of Sulfurospirillum deleyianum, and Sulfurospirillum arcachonense, form a distinct clade within the epsilon subclass of the Proteobacteria based on 16S rRNA analysis. (+info)
Simultaneous reduction of nitrate and selenate by cell suspensions of selenium-respiring bacteria.
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Washed-cell suspensions of Sulfurospirillum barnesii reduced selenate [Se(VI)] when cells were cultured with nitrate, thiosulfate, arsenate, or fumarate as the electron acceptor. When the concentration of the electron donor was limiting, Se(VI) reduction in whole cells was approximately fourfold greater in Se(VI)-grown cells than was observed in nitrate-grown cells; correspondingly, nitrate reduction was approximately 11-fold higher in nitrate-grown cells than in Se(VI)-grown cells. However, a simultaneous reduction of nitrate and Se(VI) was observed in both cases. At nonlimiting electron donor concentrations, nitrate-grown cells suspended with equimolar nitrate and selenate achieved a complete reductive removal of nitrogen and selenium oxyanions, with the bulk of nitrate reduction preceding that of selenate reduction. Chloramphenicol did not inhibit these reductions. The Se(VI)-respiring haloalkaliphile Bacillus arsenicoselenatis gave similar results, but its Se(VI) reductase was not constitutive in nitrate-grown cells. No reduction of Se(VI) was noted for Bacillus selenitireducens, which respires selenite. The results of kinetic experiments with cell membrane preparations of S. barnesii suggest the presence of constitutive selenate and nitrate reduction, as well as an inducible, high-affinity nitrate reductase in nitrate-grown cells which also has a low affinity for selenate. The simultaneous reduction of micromolar Se(VI) in the presence of millimolar nitrate indicates that these organisms may have a functional use in bioremediating nitrate-rich, seleniferous agricultural wastewaters. Results with (75)Se-selenate tracer show that these organisms can lower ambient Se(VI) concentrations to levels in compliance with new regulations proposed for release of selenium oxyanions into the environment. (+info)
Effect of selenate as a feed supplement to dairy cows in comparison to selenite and selenium yeast.
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The main aim of this trial was to define the possible differences between selenite and selenate in their ability to increase the selenium (Se) concentration of milk, in comparison with organic Se. Dairy cows (n = 42) were fed a basal diet containing .10 to .12 mg Se/kg DM for 5 mo and were then divided into four groups of 10 or 11, as similar as possible in age and stage of lactation. During the next 84 d, the cows in three of the groups were supplemented with 3 mg of Se daily, whereas the cows in one control group remained unsupplemented. The Se supplement was given as sodium selenite, sodium selenate, or a Se yeast product. The total Se concentration of the diets varied with the cows' stage of lactation and was for the supplemented groups .24 to .31 mg/kg DM, but remained between .10 and .12 mg/kg in the control group. At the end of the trial, the mean whole blood Se concentrations in the selenite, selenate, yeast, and control groups were 138, 141, 165, and 104 microg/L, respectively. The Se concentration in plasma apparently reached a plateau level within 4 wk, at approximately 75 microg/L in the selenite group, 80 microg/L in the selenate group, and 90 microg/L in the yeast group. In the control group the mean concentration in plasma remained at approximately 50 microg/L. The increase of the activity of glutathione peroxidase (GSH-Px) in the erythrocytes was significantly higher in the supplemented groups than in the control group. The mean concentrations of Se in milk in the selenite, selenate, and yeast groups were 16.4, 16.4, and 31.2 microg/L, respectively, whereas the concentration remained at approximately 14 microg/L in the control group. The milk Se concentration reached a plateau within 1 wk after the start of Se supplementation. Dietary supplementation with selenite and selenate, thus, had only a limited effect on the Se concentration in milk, and there was no significant difference between the two inorganic compounds in any variable measured. Organic Se was much more effective than inorganic Se in increasing the concentration of Se in milk. (+info)
Effects of vitamin E and selenium supplementation on esophageal adenocarcinogenesis in a surgical model with rats.
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Two well-known antioxidative nutrients, vitamin E and selenium, were used in this study to investigate possible inhibitory action against the formation of esophageal adenocarcinoma (EAC) in rats. In this model, carcinogenesis is believed to be driven by oxidative stress. Male Sprague-Dawley rats (8 weeks old) were divided into four groups and received esophagoduodenal anastomosis (EDA) surgery plus iron supplementation (12 mg/kg/week). Vitamin E and selenium were supplemented in the diet in the forms of alpha-tocopheryl acetate (750 IU/kg) and sodium selenate (1.7 mg Se/kg), which were 10 times the regular amounts in the basic AIN93M diet. At 40 weeks after surgery, all the EDA groups had lower body weights than the non-operated control group. Iron nutrition (hemoglobin, total serum iron and transferrin saturation) was normal as a result of iron supplementation after EDA. Vitamin E supplementation maintained the normal plasma level of alpha-tocopherol in EDA rats, but not those of gamma-tocopherol and retinol. Selenium supplementation increased the serum and liver selenium contents of the EDA rats. Histopathological analysis showed that selenium supplementation increased the incidence of EAC and the tumor volume. The selenium level in the tumor is higher than that in the duodenum of the same animal. Vitamin E supplementation, however, inhibited carcinogenesis, especially in the selenium-supplemented group. We believe that vitamin E exerts its effect through its antioxidative properties, and a high dose of inorganic selenium may promote carcinogenesis by enhancing oxidative stress. (+info)
Antioxidants with carcinostatic activity (resveratrol, vitamin E and selenium) in modulation of blood platelet adhesion.
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Compounds with potential antiplatelet activity can be used in the therapy of cardiovascular disorders. We investigated the effects of three different antioxidants with carcinostatic property: trans-resveratrol, Trolox a water-soluble analog of vitamin E, and inorganic selenocompounds (sodium selenite and selenate) on blood platelet adhesion to fibrinogen (Fg). Adhesion, the initial step of platelet activation, was estimated by the colorimetric method with BCA (bicinchoninic acid) solution in 96-well Fg-coated microtiter dishes. It was shown that resveratrol significantly inhibited adhesion of both thrombin- and ADP-activated platelets to Fg. After incubation of platelets for 30 min. at 37 degrees C with resveratrol at the concentration of 100 microg/ml above 40% inhibition of adhesion was achieved. The inhibition of platelet adhesion of Fg caused by Trolox was lower than by resveratrol and at higher concentration (1 mM) reached maximum 12%. We also demonstrated that neither sodium selenite nor selenate significantly altered platelet adhesion to Fg. We conclude that changed adhesion of blood platelets to Fg in the presence of resveratrol and Trolox, but not selenium may be the result of different antioxidative activities of tested compounds. (+info)
Fate of selenate and selenite metabolized by Rhodobacter sphaeroides.
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Cultures of a purple nonsulfur bacterium, Rhodobacter sphaeroides, amended with approximately 1 or approximately 100 ppm selenate or selenite, were grown phototrophically to stationary phase. Analyses of culture headspace, separated cells, and filtered culture supernatant were carried out using gas chromatography, X-ray absorption spectroscopy, and inductively coupled plasma spectroscopy-mass spectrometry, respectively. While selenium-amended cultures showed much higher amounts of SeO(3)(2-) bioconversion than did analogous selenate experiments (94% uptake for SeO(3)(2-) as compared to 9.6% for SeO(4)(2-)-amended cultures from 100-ppm solutions), the chemical forms of selenium in the microbial cells were not very different except at exposure to high concentrations of selenite. Volatilization accounted for only a very small portion of the accumulated selenium; most was present in organic forms and the red elemental form. (+info)
Inhibitory effect of selenite on invasion of HT1080 tumor cells.
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Selenium, an essential biological trace element, has been shown to reduce and prevent the incidence of cancer. Our previous studies have shown that selenite is involved in the chemoprevention of cancer and induction of apoptosis of cancer cells. In this study, we demonstrate that selenite also inhibits the invasion of tumor cells. Cancer cell invasion requires coordinated processes, such as changes in cell-cell and cell-matrix adhesion, degradation of the extracellular matrix, and cell migration. We found that selenite inhibited invasion of HT1080 human fibrosarcoma cells. Adhesion of HT1080 cells to the collagen matrix was also inhibited by treatment with selenite, but cell-cell interaction and cell motility were not affected by selenite. Moreover, selenite reduced expression of matrix metalloproteinase-2 and -9 and urokinase-type plasminogen activator, which are involved in matrix degradation, but increased a tissue inhibitor of metalloproteinase-1. This inhibitory effect of selenite on the protease expressions was mediated by the suppression of transcription factors, NF-kappaB and AP-1. However, selenate showed no remarkable effect on all the steps of cancer cell invasion. (+info)
Bordetella petrii sp. nov., isolated from an anaerobic bioreactor, and emended description of the genus Bordetella.
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A novel Bordetella species was isolated from an anaerobic, dechlorinating bioreactor culture enriched from river sediment. The only strain, Se-1111R(T) (= DSM 12804T = CCUG 43448T), for which the name Bordetella petrii is proposed, is designated the type strain of the novel species. Strain Se-1111R(T) was isolated from the dechlorinating mixed culture due to its ability to anaerobically reduce selenate to elemental selenium. Comparative 16S rDNA sequence analysis showed a close relationship between Se-1111R(T) and members of the genus Bordetella within the beta-Proteobacteria. This close phylogenetic relatedness was also reflected in several metabolic properties of Se-1111R(T), including its incapacity to utilize carbohydrates, by the high G+C content (63.8 mol%) of its DNA and by the presence of Q-8 as the major isoprenoid quinone. DNA-DNA hybridization experiments with type strains of all species of the genus Bordetella and closely related species Achromobacter xylosoxidans subsp. denitrificans provided further evidence for the assignment of strain Se-1111R(T) as a novel species of the genus Bordetella. This genus currently consists of seven aerobic species, all of which are known to occur in close pathogenic, opportunistic or possibly commensal relationships with various host organisms. B. petrii is the first member of this genus isolated from the environment and capable of anaerobic growth. The proposal of the novel species and an emended description of the genus Bordetella is presented. (+info)