Reduction Of Tetrathionate Research Articles

Solubilization and purification of a cytoplasmic membrane bound enzyme catalyzing tetrathionate and thiosulphate reduction in Proteus mirabilis.

Solubilization of cytoplasmic membrane bound tetrathionate and thiosulphate reductase was accomplished without detergents by repeated extraction of a purified cytoplasmic membrane suspension with tert-amyl alcohol. On homokinetic sucrose gradients both solubilized reductase activities banded in single peaks in the same fractions. A sedimentation constant of 6.9 Svedbergs was calculated using catalase as indicator enzyme. Further purification was obtained on an electro focusing column. Again both reductase activities banded as a single peak in the same fractions. It can be concluded that both have an isoelectric point of 5.22. It was demonstrated on polyacrylamide gels that the peak fractions contained virtually one protein component, which catalyzes tetrathionate reduction as well as thiosulphate reduction. It was concluded that Proteus mirabilis has only one enzyme for both enzymatic functions. From polyacrylamide gel electrophoresis in 0.1% sodium dodecyl sulphate it appeared that this enzyme consists of two subunits with molecular weights of approx. 43 000 and 90 000 daltons. The complete enzyme has thus a molecular weight of approx. 133 000 daltons. Protein profiles of cytoplasmic membranes isolated after various growth conditions suggest that the smaller subunit of this enzyme is present after anaerobic growth in the presence of KNO3 in spite of repression of the complete enzyme under this growth condition.

Influence of hydrogen acceptors on growth and energy production ofProteus mirabilis

The generation time ofP. mirabilis in defined and in complex medium is shorter in the presence of hydrogen acceptors than in their absence. In the presence of hydrogen acceptors the molar growth yield for glucose and the acetate production are strongly increased. From the molar growth yield and the acetate production YATP in defined medium was calculated as 5.5 g/mole, whereas in complex medium a value of 12.6 g/mole was obtained. The molar growth yield, the acetate production, the amount of hydrogen acceptor reduced and YATP were used to calculate P/2e−ratios for phosphorylation coupled to electron transfer to oxygen, nitrate and tetrathionate as respectively 2.80; 1.48 and 1.23 in defined medium. Under anaerobic conditions in the presence of nitrate or tetrathionate as hydrogen acceptor in complex medium a bend in the growth curve is observed. In the period of rapid growth the P/2e−ratio for nitrate reduction is of the same magnitude as that in defined medium, however much lower P/2e−ratios are found during the subsequent period of slow growth. The P/2e−ratios for tetrathionate reduction in complex medium for both growth periods are lower than those in defined medium. Most probably these results indicate that during this period growth and energy production are uncoupled. Under aerobic conditions in complex medium a constant YO value of 32.2 g/atom O is found during a short period of the growth curve. Afterwards when the cell density increases a steady decrease of YO is observed.

The physiological role of tetrathionate respiration in growing citrobacter.

SUMMARY: The reduction of tetrathionate to thiosulphate by anaerobically growingCitrobacter caused a significant rise in specific growth rate and molar growth yield. It enabled alsoanaerobic growth on non-fermentable carbon sources and resembled therefore the respiratory reduction of nitrate to nitrite. The efficiency of energy production by tetrathionate respiration amounted to only two-thirds that of nitrate respiration.

Kinetics of the reduction of tetrathionate by intact bacterial cells.

The kinetics of the reduction of tetrathionate by washed nongrowing intact cells ofCitrobacter were studied. The rate of the reduction in most cases is not constant. The course of reduction usually resembles the first order kinetics within a limited, varying initial time period. This finding makes it possible to evaluate quantitatively the curves obtained experimentally of the relationship between concentration of the product and time, applyingequations valid for this reaction order, to determine the rate constant of the first order reaction and thus to determine the initial rate of the reduction of tetrathionate as the measure of the tetrathionate-reductaso activity of intact cells. Deviations from the first order kinetics, observed during later phases of the reduction are caused by excessive acidification of the medium. The effect of various experimental conditions on the initial rate of reduction of tetrathionate by the cells was also studied. The results presented served as a basis of a general method for the quantitative evaluation of the tetrathionate-reductase activity of intact bacterial cells.

Some factors influencing the rate of formation of tetrathionase.

SUMMARY: The intermediate type I coliform organism 1433 can use, as hydrogen donators during the adaptive formation of the tetrathionase enzyme system, most of the carbohydrates that it can ferment, although in some cases the cells must first be grown on a medium containing the carbohydrate concerned. Not only the reduction of tetrathionate, but the process of adaptive formation of tetrathionase as well, is inhibited by oxygen gas, but the capacity to adapt when favourable conditions are restored is relatively unaffected by oxygen. The amount and the rate of formation of new enzyme are greatly increased by providing a source of available nitrogen. The rate of formation is also increased by incubating the cells with mannitol and phosphate before tetrathionate is added, but the total amount of enzyme formed is not increased: it is probable that the increased rate is due to the accumulation of intermediates within the cells; these intermediates have not so far been identified. None of the mathematical expressions investigated fits the course of tetrathionase adaptation exactly; that put forward by Spiegelman (1945) for the production of yeast galactozymase approximates most closely.

Bacterial reduction of tetrathionate

Research Article| October 01 1943 Bacterial reduction of tetrathionate: A report to the medical research council M. R. Pollock; M. R. Pollock 1Emergency Public Health Laboratory, Leicester Search for other works by this author on: This Site PubMed Google Scholar R. Knox R. Knox 1Emergency Public Health Laboratory, Leicester Search for other works by this author on: This Site PubMed Google Scholar Biochem J (1943) 37 (4): 476–481. https://doi.org/10.1042/bj0370476 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation M. R. Pollock, R. Knox; Bacterial reduction of tetrathionate: A report to the medical research council. Biochem J 1 October 1943; 37 (4): 476–481. doi: https://doi.org/10.1042/bj0370476 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Journal Search Advanced Search This content is only available as a PDF. © 1943 CAMBRIDGE UNIVERSITY PRESS1943 Article PDF first page preview Close Modal You do not currently have access to this content.

Bacterial Reduction of Tetrathionate

THE power of reducing nitrate is widespread among micro-organisms, while the reduction of sulphate is restricted to a few species1. It has long been recognized, however, that many bacteria are able to reduce less highly oxidized inorganic sulphur compounds (tetrathionate, thiosulphate, sulphite, etc.) to hydrogen sulphide2. In the course of attempts to improve selective media for isolating Salmonellas and Bact. typhosum from excreta, we have found that, so far as some organisms are concerned, the tetrathionate is first reduced to thiosulphate. This reaction takes place rapidly and quantitatively, and estimations at different stages show that the molecular concentration of the thiosulphate formed is twice that of the tetrathionate which has disappeared, in agreement with the equation: The subsequent further reduction of thiosulphate to hydrogen sulphide is, in comparison, so slow that the reduction of tetrathionate can be followed accurately by direct iodometric titration of the thiosulphate, provided that the high acidity developing from accumulat on of thiosulphuric acid is controlled by a phosphate buffer.