Universiẗat, Diss., 2001--München.

Universiẗat, Diss., 2002--Frankfurt (Main).

<p> The extremely halophilic bacterium, Halobacterium salinarium, contains a light density satellite DNA component which is 20% of the total DNA. </p> <p> The purpose of this investigation was to study the physical characteristics of the satellite DNA by ultra- centrifugation and electron microscopic methods in an attempt to answer the following questions: "(a) Does the amount of the satellite depend on DNA isolation conditions?" "(b) What is the biological derivation of the satellite?" "(c) What is the physical size( s) of the satellite?" "(d) How many copies of the satellite occur in the"cell?" </p> <p> The results of this investigation showed that the amount of the satellite is independent of isolation conditions, and that it exists in the form of closed circular duplexes. Although the possibility that the satellite represents multiple forms of closed circular molecules could not be completely ruled out, the majority of the closed circles appeared to have lengths about 37 u, so that there might be eight copies of the satellite per bacterial genome. </p> / Thesis / Master of Science (MSc)

No description available.

Bochum, Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Bochum, Universiẗat, Diss., 2003.

No description available.

Several new pterins have been discovered in halophilic and thermoacidophilic archaebacteria. Two of these were identified in the extreme halophiles and were thus called halopterins. One of these halopterins is produced by Halobacterium salinarium, Halobacterium halobium, and Halococcus morrhuae and is called phosphohalopterin-1. It was given this name because it was the first halopterin discovered and it has four monophosphate esters per dimeric pterin. The proposed structure of phosphohalopterin-1 is as follows. [see document for diagram of chemical structure] The other halopterin, which is produced by Halobacterium marismortui, Halobacterium volcanii, and Halobacterial strain GN-1, is called sulfohalopterin-2 because it has two sulfate esters per dimeric pterin and it was isolated and recognized after the isolation of phosphohalopterin-1. The proposed structure of sulfohalopterin-2 is as follows. [see document for diagram of chemical structure] As shown above, both pterins are dimers with an ether linkage connecting the polyol side chains. Both of the halopterins are negatively charged because of the phosphate and sulfate esters on the side chains. In addition to the halopterins, a positively charged pterin has been isolated from Sulfolobus solfataricus. This pterin is very special since no positively charged unconjugated pterin had ever been found in nature before. This pterin is named solfapterin after the species name of the bacteria from which it was obtained. The structure of this pterin is still unknown but the preliminary data indicate that it is an unconjugated pterin with a polyol containing an amine on the side chain. Another positively charged pterin which is different from solfapterin was found in Thermoplasma. All of the above pterins are different from any previously described pterins and thus represent new pterins in the archaebacterial kingdom. The discovery of these new pterins is important both to pterin biochemistry and to archaebacterial taxonomy. These discoveries also open up a new field, that is, the exploration of the function of these new pterins in norunethanogenic archaebacteria. / Ph. D.

<p>The regulation of metabolism is one of the key challenges faced by organisms across all domains of life. Despite fluctuating environments, cells must produce the same metabolic outputs to thrive. Although much is known about the regulation of metabolism in the bacteria and the eukaryotes, relatively little is known about the regulation of metabolism in archaea. Previous work identified the winged helix-turn-helix transcription factor TrmB as a major regulator of metabolism in the model archaeon Halobacterium salinarum. TrmB was found to bind to the promoter of 113 genes in the absence of glucose. Many of these genes encode enzymes involved in metabolic processes, including central carbon metabolism, purine synthesis, and amino acid degradation. Although much is known about TrmB, it remains unclear how it dynamically regulates its ~100 metabolic enzyme-coding gene targets, what the effect of transcriptional regulation is on metabolite levels, and why TrmB regulates so many metabolic processes in response to glucose. Using dynamic gene expression and TrmB-DNA binding assays, we found that that TrmB functions alone to regulate central metabolic enzyme-coding genes, but cooperates with various regulators to control peripheral metabolic pathways. After determining the temporal pattern of gene expression changes and their dependence on TrmB, we used dynamic metabolite profiling to investigate the effects of transcriptional changes on metabolite levels and phenotypes. We found that TrmB-mediated transcriptional changes resulted in substantial changes in metabolite levels. Additionally, we showed that mis-regulation of genes encoding enzymes involved in gluconeogenesis in the &#916;trmB mutant strain in the absence of glucose results in low PRPP levels, which cause a metabolic block in de novo purine synthesis that is partially responsible for the growth defect of the &#916;trmB mutant strain. Finally, using a series of quantitative phenotyping experiments, we showed that TrmB regulates the gluconeogenic production of sugars incorporated into the cell surface S-layer glycoprotein. Because S-layer glycosylation is proportional to growth, we hypothesize that TrmB transduces a growth rate signal to co-regulated metabolic pathways including amino acid, purine, and cobalamin biosynthesis. Taken together, our results suggest that TrmB is a global regulator of archaeal metabolism that works in concert with other transcription factors to regulate diverse metabolic pathways in response to nutrients and growth rate.</p> / Dissertation

Universiẗat, Diss., 2000--München.