Quaternary sediment patterns in the Weddell Sea: relations and environmental conditions

Sediment patterns such as texture, composition, and facies from three selected areas of the Antarctic continental margin of the Weddell Sea are discussed in relation to environmental variations of the Quaternary hydrosphere and kryosphere. Advance and retreat of ice shelves as well as oscillations in sea ice coverage are reflected by particular sediment facies. The distribution of ice-rafted detritus tracks the Antarctic Coastal Current, and the Weddell Sea Bottom water contour current can be recognized by its distinctive winnowing and erosion pattern. Distribution and abundance of biogenic sediment components are mainly controlled by duration of sea ice coverage reflecting the long-term climatic evolution

Methodological contributions to the challenges and opportunities of high dimensional clustering in the context of single-cell data

With the sequencing of single cells it is possible to measure gene expression of each single-cell in contrast to bulk sequencing which enables only average gene expression. This procedure provides access to read counts for each single cell and allows the development of methods such that single cells are automatically allocated to cell types. The determination of cell types is decisive for the analysis of diseases and to understand human health based on the genetic profile of single cells. It is of common use that cell types are allocated using clustering procedures that have been developed explicitly for single-cell data. For that purpose the single-cell consensus clustering (SC3), proposed by Kiselev et al. (Nat Methods 14(5):483-486, 2017) is part of the leading clustering methods in this context and is also of relevance for the following contributions. This PhD thesis aims at the development of appropriate analysis techniques for the clustering of high-dimensional single-cell data and their reliable validation. It also provides a simulation framework for the investigation of the influence of distorted measurements of single cells towards clustering performance. We further incorporate cluster indices as informative weights into the regularized regression, which allows a soft filtering of variables

PANGAEA information system for glaciological data management

Specific parameters determined on cores from continental ice sheets or glaciers can be used to reconstruct former climate. To use this scientific resource effectively an information system is needed which guarantees consistent longtime storage of data and provides easy access for the scientific community.An information system to archive any data of paleoclimatic relevance, together with the related metadata, raw data and evaluated paleoclimatic data, is presented. The system, based on a relational database, provides standardized import and export routines, easy access with uniform retrieval functions, and tools for the visualization of the data. The network is designed as a client/server system providing access through the Internet with proprietary client software including a high functionality or read-only access on published data via the World Wide Web

Geminivirus sequences as bidirectional transcription termination/polyadenylation signals for economic construction of stably expressed transgenes

Bidirectional, convergent transcription of transgenes in transgenic plants can occur due to leaky transcription termination of separate convergent genes or from genomic promoters. It might also be engineered with the purpose of generating double-stranded RNA to downregulate genes by RNA interference. We have tested the effects of convergent transcription on expression levels and analysed the potential of geminivirus derived DNA sequences to act as bidirectional transcription termination/polyadenylation signals in transgenes to counteract such negative effects. Convergent, overlapping transcription decreased expression, however, no increased propensity for induction of gene silencing was observed. The geminivirus terminators in both orientations supported efficient expression of single genes and of convergent genes, whereas a unidirectional terminator allowed only reduced expression in this latter situation. Geminivirus terminators could be used as efficient transcription control element for the expression of two genes simultaneously or, with single genes, could afford protection of the gene against unwanted anti-sense transcription from transcription units downstream of the gene, e.g. in the integration locus. Our results also suggest that flanking of a given sequence by two convergent promoters would not be an efficient way to generate double-stranded RNA and induce gene silencing by RNA

Platensimycin Activity against Mycobacterial β-Ketoacyl-ACP Synthases

Background - There is an urgent need for the discovery and development of new drugs against Mycobacterium tuberculosis, the causative agent of tuberculosis, especially due to the recent emergence of multi-drug and extensively-drug resistant strains. Herein, we have examined the susceptibility of mycobacteria to the natural product platensimycin. Methods and Findings - We have demonstrated that platensimycin has bacteriostatic activity against the fast growing Mycobacterium smegmatis (MIC = 14 µg/ml) and against Mycobacterium tuberculosis (MIC = 12 µg/ml). Growth in the presence of paltensimycin specifically inhibited the biosynthesis of mycolic acids suggesting that the antibiotic targeted the components of the mycolate biosynthesis complex. Given the inhibitory activity of platensimycin against β-ketoacyl-ACP synthases from Staphylococcus aureus, M. tuberculosis KasA, KasB or FabH were overexpressed in M. smegmatis to establish whether these mycobacterial KAS enzymes were targets of platensimycin. In M. smegmatis overexpression of kasA or kasB increased the MIC of the strains from 14 µg/ml, to 30 and 124 µg/ml respectively. However, overexpression of fabH on did not affect the MIC. Additionally, consistent with the overexpression data, in vitro assays using purified proteins demonstrated that platensimycin inhibited Mt-KasA and Mt-KasB, but not Mt-FabH. Significance - Our results have shown that platensimycin is active against mycobacterial KasA and KasB and is thus an exciting lead compound against M. tuberculosis and the development of new synthetic analogues