Deferribacter desulfuricans sp. nov., a novel sulfur-, nitrate- and arsenate-reducing thermophile isolated from a deep-sea hydrothermal vent.
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A novel anaerobic, heterotrophic thermophile was isolated from a deep-sea hydrothermal vent chimney at the Suiyo Seamount in the Izu-Bonin Arc, Japan. The cells were bent, flexible rods, with a single polar flagellum. Growth was observed between 40 and 70 degrees C (optimum temperature: 60-65 degrees C; doubling time, 40 min) and between pH 5.0 and 7.5(optimum pH 6.5). The isolate was a strictly anaerobic heterotroph capable of using complex organic compounds (yeast extract, tryptone, peptone, casein and Casamino acids), ethanol and various organic acids as energy and carbon sources. Hydrogen could serve as a supplementary energy source. Elemental sulfur (S(0)), nitrate or arsenate was required for growth as an electron acceptor. The G + C content of the genomic DNA was 38.6 mol%. Phylogenetic analysis based on 16S rDNA sequences indicated that isolate SSM1(T) is closely related to Deferribacter thermophilus BMA(T) (98.1%). However, the novel isolate could be clearly differentiated from D. thermophilus BMA(T) on the basis of its physiological and genetic properties. The name Deferribacter desulfuricans sp. nov. (type strain SSM1(T) = JCM 11476(T) = DSM 14783(T)) is proposed. (+info)
Nature of the energy requirement for the irreversible adsorption of bacteriophages T1 and phi80 to Escherichia coli.
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The nature of the energy requirement for irreversible adsorption of phages T1 and phi80 was studied by using various specific energy inhibitors and mutants lacking either the Ca2+, Mg2+-adenosine triphosphatase or the ability to produce cytochromes in the absence of added 5-aminolaevulinic acid. It was found that irreversible adsorption could be energized both through the electron transport chain and from adenosine 5'-triphosphate via the Ca2+, Mg2+-adenosine triphosphatase, indicating the involvement of the energized membrane state. These results and the discovery that phages T1 and phi80 adsorb reversibly to the isolated tonA gene product are discussed in terms of the possible involvement of functions expressed by the tonB gene region in irreversible adsorption and the relationship to iron transport. (+info)
The distribution of arsenate and arsenite in shoots and roots of Holcus lanatus is influenced by arsenic tolerance and arsenate and phosphate supply.
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The recent discovery that phytochelatins are important for arsenic (As) detoxification in terrestrial plants results in the necessity to understand As speciation and metabolism in plant material. A hydroponic study was therefore conducted to examine the effects of different levels of phosphate and arsenate [As(V)] on As speciation and distribution in tolerant and non-tolerant clones of Holcus lanatus. Speciation of As in tissue (using high-performance liquid chromatography-inductively coupled plasma mass spectrometry) revealed that the predominant species present were the inorganic As species (As(V) and arsenite [As(III)]), although small levels (<1%) of organic As species (dimethylarsinic acid and monomethylarsonic acid) were detected in shoot material. In roots, the proportion of total As present as As(III) generally increased with increasing levels of As(V) in the nutrient solution, whereas in shoots, the proportion of total As present as As(III) generally decreased with increasing levels of As(V). H. lanatus plants growing in the high-phosphorus (P) (100 micro M) solution contained a higher proportion of As(V) (with regard to total As) in both roots and shoots than plants supplied with low P (10 micro M); in addition, tolerant clones generally contained a higher proportion of As(V) with regard to total As than non-tolerant clones. The study further revealed that As(V) can be reduced to As(III) in both roots and shoots. Although the reduction capacity was limited, the reduction was closely regulated by As influx for all treatments. The results therefore provide a new understanding about As metabolism in H. lanatus. (+info)
Transport of vitamin B12 in Escherichia coli: energy dependence.
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This paper presents some evidence that the osmotic shock-sensitive, energy-dependent transfer of vitamin B12 from outer membrane receptor sites into the interior of cells of Escherichia coli requires an energized inner membrane, without obligatory intermediation of adenosine 5'-triphosphate (ATP). The experiments measured the effects of glucose, D-lactate, anaerobiosis, arsenate, cyanide, and 2,4-dinitrophenol upon the rates of B12 transport by starved cells of E. coli KBT001, which possesses a functional Ca2+, Mg2+-stimulated adenosine triphosphatase (Ca,MgATPase), and of E. coli AN120, which lacks this enzyme. Both strains were able to utilize glucose and D-lactate aerobically to potentiate B12 transport, indicating that the Ca,MgATPase was not essential for this process. When respiratory electron transport was blocked, either by cyanide or by anaerobic conditions, and the primary source of energy for the cells was presumably ATP from glucose fermentation, the rate of B12 transport was much reduced in E. coli AN120 but not in E.coli KBT001. These results support the view that the CaMgATPase can play a role in B12 transport but only when the energy for this process must be derived from ATP. The results of experiments with arsenate also supported the conclusion that the generation of phosphate bond energy was not absolutely required for B12 transport. (+info)
Phosphate transport into brush-border membrane vesicles isolated from rat small intestine.
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Uptake of Pi into brush-border membrane vesicles isolated from rat small intestine was investigated by a rapid filtration technique. The following results were obtained. 1. At pH 7.4 in the presence of a NaCl gradient across the membrane (sodium concentration in the medium higher than sodium concentration in the vesicles), phosphate was taken up by a saturable transport system, which was competitively inhibited by arsenate. Phosphate entered the same osmotically reactive space as D-glucose, which indicates that transport into the vesicles rather than binding to the membranes was determined. 2. The amount of phosphate taken up initially was increased about fourfold by lowering the pH from 7.4 to 6.0.3. When Na+ was replaced by K+, Rb+ or Cs+, the initial rate of uptake decreased at pH 7.4 but was not altered at pH 6.0.4. Experiments with different anions (SCN-,Cl-, SO42-) and with ionophores (valinomycin, monactin) showed that at pH 7.4 phosphate transport in the presence of a Na+ gradient is almost independent of the electrical potential across the vesicle membrane, whereas at pH 6.0 phosphate transport involves the transfer of negative charge. It is concluded that intestinal brush-border membranes contain a Na+/phosphate co-transport system, which catalyses under physiological conditions an electroneutral entry of Pi and Na+ into the intestinal epithelial cell. In contrast with the kidney, probably univalent phosphate and one Na+ ion instead of bivalent phosphate and two Na+ ions are transported together. (+info)
Uptake of ferrienterochelin by Escherichia coli: energy dependent stage of uptake.
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The uptake of the siderophore-iron complex ferrienterochelin was found to be strongly dependent upon an energized membrane state, as demonstrated by its sensitivity to dinitrophenol, azide, and cyanide. Ferrienterochelin uptake may also be dependent upon phosphate bond energy, as indicated by sensitivity to arsenate and iodoacetic acid. Although the adenosine triphosphatase does not appear to be involved in this energy coupling mechanism, ferrienterochelin uptake was shown to be less dependent upon phosphate bond energy than was glutamine uptake. Sensitivity of ferrienterochelin uptake to osmotic shock was shown to be due to the release of a ferrienterochelin binding compound located in the outer membrane of the cells and probably identical to the colicin B receptor protein. (+info)
Reduction of arsenate to arsenite by the ArsC protein of the arsenic resistance operon of Staphylococcus aureus plasmid pI258.
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The arsenic resistance operon of Staphylococcus aureus plasmid pI258 consists of three genes, arsR (encoding the repressor regulatory protein), arsB (the determinant of the membrane efflux protein that confers resistance by pumping arsenic from the cells), and arsC (the small gene whose protein product is required for arsenate resistance only, not for arsenite resistance). ArsC has now been shown to be an arsenate reductase, converting intracellular arsenate [As(V)] to arsenite [As(III)], which is then exported from the cells by an energy-dependent efflux process. The arsenate reductase activity was found in the soluble cytoplasmic fraction in Escherichia coli (and not associated with the periplasmic fraction or the sedimentable cell envelope). Purified ArsC protein coupled in vitro with thioredoxin plus dithiothreitol (but not 2-mercaptoethanol or reduced glutathione) to reduce arsenate to arsenite. (+info)
Phosphate transport by capillaries of the blood-brain barrier.
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Capillaries were isolated from bovine brain cortex and used for phosphate transport studies. The influx of phosphate through capillary membranes was studied by incubation with [32Pi]phosphate followed by a rapid filtration technique. Phosphate uptake by brain capillaries was mediated by a saturable high-affinity system which is independent of the sodium concentration in the incubation medium. The apparent half-saturation constant (Km) and maximal influx (Vmax) were estimated to 160 microM and 0.37 nmol/mg protein/30 s. Transport was inhibited by the phosphate analogues arsenate and phosphonoformic acid with apparent inhibition constants of 5 and 11 mM, respectively. The metabolic inhibitors cyanide and ouabain had no effect on the transport activity. Competition experiments showed that phosphate uptake was inhibited up to 41% by various anions (pyruvate, acetate, citrate, glutamate, and sulfate). In addition, phosphate uptake was significantly decreased by two selective inhibitors of anionic exchangers, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid. Chloride was not a substrate of the phosphate carrier as the replacement of external chloride, by nitrate, thiocyanate, or gluconate, did not increase phosphate transport. Aminohippuric acid and N'-methylnicotinamide, two specific substrates of anionic and cationic drug exchangers, did not compete with the phosphate carrier of cerebral capillaries. However, trans-stimulation with bicarbonate increased phosphate transport by 28%, and this stimulation was inhibited by 1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, suggesting that the carrier of the cerebral capillaries could exchange phosphate with bicarbonate. (+info)