Schulz-Vogt, Heide
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Schulz-Vogt, Heide
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Item-typ:Veröffentlichung, Physiology of a marine Beggiatoa strain and the accompanying organism Pseudovibrio sp. - a facultatively oligotrophic bacterium(2011-10-31); ; ; Large filamentous sulfide-oxidizing bacteria are capable of forming huge microbial mats at the oxic-anoxic interface of the sediment surface. The first part of this thesis shows that a subpopulation of Beggiatoa filaments actively migrates into anoxic, sulfidic layers as a reaction to high sulfide fluxes. The reason for this so far unknown migration behavior seems to be excessive storage of reserve compounds. By moving into anoxic regions, aerobic sulfide oxidation is stopped and storage space is emptied by reducing the stored sulfur with carbon reserve compounds. The association of the sulfide-oxidizer and a small heterotrophic bacterium (Pseudovibrio sp.) is investigated in the second part of this thesis. In contrast to the large Beggiatoa sp., the Pseudovibrio sp. is able to grow in pure culture under extremely oligotrophic conditions. Under oligotrophic conditions we found that Pseudovibrio sp. grows on organic contaminations preferentially containing nitrogen.Dissertation337 136 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Electron donors and acceptors for members of the family Beggiatoaceae(2013-12-16); ; ; The family Beggiatoaceae comprises large, colorless sulfur bacteria, which are best known for their chemolithotrophic metabolism, the oxidation of reduced sulfur compounds with oxygen or nitrate. This thesis contributes to a more comprehensive understanding of the ecophysiology of these organisms with several studies on different aspects of their dissimilatory metabolism. Section 2 proposes a general model of sulfur compound oxidation in this family and Section 3 presents a possible rationale for sulfur respiration under strongly sulfidic conditions. Section 4 describes physiological and genomic studies, showing that members of the family Beggiatoaceae can use molecular hydrogen as an electron donor. The possible influence of hydrogen oxidation on the metabolic plasticity of the Beggiatoaceae is discussed and environmental settings are pointed out, in which hydrogen oxidation could be important for these organisms. Section 5 compares the energetics of hydrogen and sulfur oxidation.Dissertation362 170 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Impact of sulfide-oxidizing bacteria on the phosphorus cycle in marine sediments(2011-02-28); ; ; Studies with the marine Beggiatoa strain 35Flor revealed that intracellular polyphosphate is rapidly degraded and phosphate is released in response to a switch from oxic to anoxic conditions at high sulfide concentrations. This new mode of polyphosphate usage drastically increases phosphate concentrations in the surrounding medium and helps to explain high phosphate concentrations in organic rich sediments of coastal upwelling areas, which enhance the chance of apatite precipitation. The unusually large polyphosphate inclusions in Beggiatoa strain 35Flor represent a new type of storage compartment within the family Beggiatoaceae, aside of aqueous vacuoles that mostly contain nitrate. They are enclosed by a vacuolar membrane and contain cations such as calcium and magnesium. Furthermore, a Beggiatoa-induced decrease of uranium concentrations in natural seawater was observed.Dissertation260 326 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Physiology of Pseudovibrio sp. FO-BEG1 - a facultatively oligotrophic and metabolically versatile bacterium(2012-03-29); ; ; Bacteria belonging to the genus Pseudovibrio are frequently found in marine habitats, mainly in association with sponges, corals and tunicates. Particularly sponges harbor populations of Pseudovibrio spp.-related bacteria, which led to the proposal that this genus contains sponge symbionts. However, the physiology of the genus Pseudovibrio is insufficiently studied and hardly anything is known about its relevance in the environment. In the course of this thesis, the Pseudovibrio strain FO-BEG1 was investigated. It had previously been enriched together with the sulfide oxidizing Beggiatoa sp. 35Flor from a black band diseased coral and was eventually cultured axenically, permitting sequencing of the genome as well as metabolic studies and investigations of physiological changes under different growth conditions.Dissertation265 290 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Diversity studies and molecular analyses with single cells and filaments of large, colorless sulfur bacteria(2011-06-06); ; ; Large sulfur bacteria feature conspicuous morphologies that are usually visible with the naked eye. Most representatives were already described in the 19th and early 20th century and it needed nearly another 100 years until a new morphotype of large sulfur bacteria was discovered. This discovery encouraged a search for other yet unknown types in this group of bacteria and indeed led to the finding of a new type in two marine seep settings. This novel morphotype is presented in Chapter 2 and is the first non-filamentous member in the family Beggiatoaceae that shows a dimorphic life cycle, exhibiting alternation between sessile and free-living forms. In Chapter 3, another three novel morphotypes are presented, which were discovered in Namibian sediments. The detection of these novel morphotypes of large sulfur bacteria led to the necessity for an improved phylogenetic classification of the entire group. Earlier attempts to sequence the 16S rRNA genes of the large sulfur bacteria resulted in only few nearly full-length sequences, whereas some genera were even represented by only partial sequences. Accordingly, differentiation of genera in this group is still based on morphological features. Now, Chapter 3 presents the sequencing of 16S rRNA genes and ITS regions of more than 100 individual cells and filaments of large sulfur bacteria, revealing a major insight into the phylogeny of these extraordinary bacteria. It is demonstrated that the traditional, morphology-based classification does not correlate with the phylogeny derived from 16S rRNA gene sequences. Consequently, a reclassification of the entire family is proposed, being completely independent from former morphological categories. Sequencing single cells and filaments of large sulfur bacteria furthermore revealed that they represent the first group of bacteria, which commonly contain large and numerous introns in their 16S rRNA genes. In Chapter 4, it is demonstrated that the introns are removed efficiently from the rRNA precursor, thereby ligating the two exons, and are not present in the native ribosome. Furthermore, it was experimentally verified that a commonly applied PCR approach introduces a length heterogeneity bias and systematically discriminates against enlarged genes and favors the amplification of shorter homologues. Consequently, this fact questions the universality of 16S rRNA-based clone libraries for diversity studies. At least the group of large sulfur bacteria is systematically discriminated against in such universal PCR approaches and it can be assumed that this PCR bias also affects a yet unknown amount of other microorganisms.Dissertation305 151 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Polyphosphate storage in the family Beggiatoaceae with a focus on the species Beggiatoa alba(2013-10-23); ; ; Sulfur bacteria of the family Beggiatoaceae are of special interest with respect to the phosphorus cycle, because they can store large amounts of polyphosphate and are proposed to influence phosphorus sequestration in marine sediments (e.g. Schulz and Schulz, 2005). The aim of this thesis was to study different aspects of polyphosphate storage in members of the family Beggiatoaceae especially on a physiological but also on genomic level with a special focus on the heterotrophic freshwater strain Beggiatoa alba B15LD.Dissertation348 258