Chemiosmotic Coupling in Methanobacterium thermoautotrophicum:Hydrogen-Dependent Adenosine 5'-Triphosphate Synthesis by Subcellular Particles

Hydrogenase and the adenosine 5'-triphosphate (ATP) synthetase complex, two enzymes essential in ATP generation in Methanobacterium thermoautotrophicum, were localized in internal membrane systems as shown by cytochemical techniques. Membrane vesicles from this organism possessed hydrogenase and adenosine triphosphatase (ATPase) activity and synthesized ATP driven by hydrogen oxidation or a potassium gradient. ATP synthesis depended on anaerobic conditions and could be inhibited in membrane vesicles by uncouplers, nigericin, or the ATPase inhibitor N,N'-dicyclohexylcarbodiimide. The presence of an adenosine 5'-diphosphate-ATP translocase was postulated. With fluorescent dyes, a membrane potential and pH gradient were demonstrated

A stable genetic polymorphism underpinning microbial syntrophy

Syntrophies are metabolic cooperations, whereby two organisms co-metabolize a substrate in an interdependent manner. Many of the observed natural syntrophic interactions are mandatory in the absence of strong electron acceptors, such that one species in the syntrophy has to assume the role of electron sink for the other. While this presents an ecological setting for syntrophy to be beneficial, the potential genetic drivers of syntrophy remain unknown to date. Here, we show that the syntrophic sulfate-reducing species Desulfovibrio vulgaris displays a stable genetic polymorphism, where only a specific genotype is able to engage in syntrophy with the hydrogenotrophic methanogen Methanococcus maripaludis. This 'syntrophic' genotype is characterized by two genetic alterations, one of which is an in-frame deletion in the gene encoding for the ion-translocating subunit cooK of the membrane-bound COO hydrogenase. We show that this genotype presents a specific physiology, in which reshaping of energy conservation in the lactate oxidation pathway enables it to produce sufficient intermediate hydrogen for sustained M. maripaludis growth and thus, syntrophy. To our knowledge, these findings provide for the first time a genetic basis for syntrophy in nature and bring us closer to the rational engineering of syntrophy in synthetic microbial communities

The Reader Strikes Back:A Narratological Approach to Paul Auster’s The New York Trilogy

The detective novel genre has long been a genre of conventions. Paul Auster’s The New York Trilogy is a detective story with a twist that challenges the established conventions of the genre. In this essay, I will use narratology, with a focus on Roland Barthes’ S/Z, to study Auster’s text. I will show that it is by using the five codes that Barthes presents in S/Z, that I am able to display how Auster challenges the conventions. In this reading I will also relate The New York Trilogy to other detective fiction and to Barthes’ notion of ‘the death of the author’. Ultimately, I will show that Auster does confirm ‘the death of the author’. In the narratives the author is disseminated step by step, and eventually ceases to play an important role

Transformation of carbon tetrachloride in an anaerobic packed-bed reactor without addition of another electron donor

Carbon tetrachloride (52 μM) was biodegraded for more than 72% in an anaerobic packed-bed reactor without addition of an external electron donor. The chloride mass balance demonstrated that all carbon tetrachloride transformed was completely dechlorinated. Chloroform and dichloromethane were sometimes also found as transformation products, but neither accumulated to significant levels in comparison to the amount of carbon tetrachloride transformed. Transformation of carbon tetrachloride in the absence of an added electron donor suggests that carbon tetrachloride itself is the source of energy for the biological reaction observed, and possibly the source of carbon for cell growth. No such mechanism is yet known. The pathway of carbon tetrachloride transformation is not clear; it may be dehalogenated by hydrolytic reduction to carbon monoxide or formic acid which are electron demanding transformations. Carbon monoxide or formic acid may be further utilized and serve as electron donor. Complete dechlorination of carbon tetrachloride according to this pathway is independent of a second electron donor or electron acceptor, as with a fermentation process. Vancomycin, an inhibitor of gram positive eubacteria, severely inhibited carbon tetrachloride transformation in batch incubations with an enrichment culture from the reactor, indicating that gram positive eubacteria were involved in carbon tetrachloride transformation. Batch experiments with bromoethanesulfonic acid, used to inhibit methanogens, and molybdate, an inhibitor of sulfate reduction in sulfate reducing bacteria, demonstrated that neither methanogens nor sulfate reducers were involved in the complete dechlorination of carbon tetrachloride

Transformation of carbon tetrachloride under sulfate reducing conditions

The removal of carbon tetrachloride under sulfate reducing conditions was studied in an anaerobic packed-bed reactor. Carbon tetrachloride, up to a concentration of 30 mu M, was completely converted. Chloroform and dichloromethane were the main transformation products, but part of the carbon tetrachloride was also completely dechlorinated to unknown products. Gram-positive sulfate-reducing bacteria were involved in the reductive dechlorination of carbon tetrachloride to chloroform and dichloromethane since both molybdate, an inhibitor of sulfate reduction, and vancomycin, an inhibitor of gram-positive bacteria completely inhibited carbon tetrachloride transformation. Carbon tetrachloride transformation by these bacteria was a cometabolic process and depended on the input of an electron donor and electron acceptor (sulfate). The rate of carbon tetrachloride transformation by sulfate reducing bacteria depended on the type of electron donor present. A transformation rate of 5.1 nmol.ml(-1).h(-1) was found with ethanol as electron donor. At carbon tetrachloride concentrations higher than 18 mu M, sulfate reduction and reductive dechlorination of carbon tetrachloride decreased and complete inhibition was observed at a carbon tetrachloride concentration of 56.6 mu M. It is not clear what type of microorganisms were involved in the observed partial complete dechlorination of carbon tetrachloride. Sulfate reducing bacteria probably did not play a role since inhibition of these bacteria with molybdate had no effect on the complete dechlorination of carbon tetrachloride