Proefschrift Rijksuniversiteit Limburg. / Met lit. opg. - Met een samenvatting in het Nederlands.

Proefschrift Maastricht. / Met lit. opg. en samenvatting in het Nederlands.

Proefschrift Universiteit Maastricht. / Met bibliogr., lit. opg. - Met samenvatting in het Nederlands.

Thesis (Ph. D.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains x, 138 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 108-136).

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

No description available.

Bracken environments harbour the sheep tick (Ixodes ricinus), known vector of a number of diseases. Initial investigation indicated the presence of sheep ticks infected with the Lyme disease spirochaete Borrelia burgdorferi on open moorland areas of the North York Moors and the moorland areas of the South West of the U.K. Some aspects of the problem of Lyme disease on U.K. moorlands were explored in this study. A survey through the summer of 1993 of people using the North York Moors, Dartmoor and the Quantock Hills in Somerset for both work and leisure activities revealed a very high proportion of people (76% of respondents had not heard of Lyme disease) who were unaware of the risk of Lyme disease or of how they might reduce that risk. An examination of three moorland vegetation communities as optimal tick habitats suggested that immature ticks are less dense on heather dominated communities than on either bracken or on Vaccinium dominated communities, and that this may be influenced by the fauna using heather dominated areas. Vaccinium sites showed high densities of all life stages of the sheep tick, as did bracken dominated sites. Ticks were collected throughout the winter months on South Western sites, but not on the North York Moors, emphasising the year round risk from infected ticks in the South West of the U.K. Vegetation management practices as tick control or reduction options in these moorland areas were investigated. Asulam spraying on bracken almost totally removed the above ground frond cover, substantially reduced live buds on the rhizome, but failed to reduce the rhizome dry weight. The density of frond cover was not affected by cutting, height and dry frond weight were reduced, live rhizome buds reduced in number and rhizome dry weight reduced. Short term control of bracken fronds was achieved by both treatments, but neither treatment provided sufficiently conclusive results on which to base long term recommendations. Comprehensive plans for after care on treated sites need to be in place before treatment is carried out. Tick densities were recorded over a two year period on these treated bracken sites. There was a proportional reduction in all tick life stages between 1993 and 1994 on sites sprayed with asulam and on cut sites compared with control sites. Although not statistically significant these results suggested that the methods of bracken control investigated in this study could influence sheep tick densities in the short term.

Universiẗat, Diss., 2005--Würzburg.

The tick-borne Lyme disease, caused by the bacterium Borrelia burgdorferi, as well as some other Borrelia species, is the subject of a dispute as to whether its conditions persist following recommended antibiotic treatment lasting no more than three weeks. Advocates for the existence of chronic Lyme disease point to numerous animal models that show some traces of the bacteria remaining after treatment and call for both the long term use of antibiotics and for the disease to be recognized as chronic and to be diagnosed more expediently. Opponents of the existence of chronic Lyme disease argue that the scientific evidence for these arguments is insufficient, citing that long term symptoms are actually signs of other diseases erroneously grouped with Lyme, that current antibiotic regimens suffice for Lyme disease treatment, and that additional antibiotics beyond current treatments provide no increase in beneficial outcomes. The evidence currently is insufficient to support many of the claims by supporters of chronic Lyme disease and further studies must be done before evidence from the animal models can be applied to human patients. The fact that Borrelia burgdorferi in particular, and perhaps other members of the Borrelia genus, has evolved many singularly peculiar traits such as a lack of reliance on iron and a large extrachromosomal genome suggest that it is not outside the realm of possibility that there is some other facet of Lyme disease not currently recognized or understood. Future exploration is needed to fully understand mechanisms of pathogenesis of this bacterium in order to either confirm or deny the ability of Lyme disease to persist in humans following treatment.

Borrelia burgdorferi — the causative agent of Lyme borreliosis — accounts for ~500,000 infections in the United States per year. Relative to other bacteria, B. burgdorferi is highly unusual in many regards. For instance, the synthesis and composition of B. burgdorferi cell wall is extremely unique and plays a critical role in Lyme pathogenesis. The cell wall is made up of peptidoglycan (PG) - a mesh-like structure, composed of long rigid glycan strands of repeating sugars GlcNAc and MurNAc, and flexible peptide stems, interlinked by amino acid cross-bridges. PG is an essential component for survival of the bacterial cell, protecting it from the osmotic stress and environmental threats, as well as defining the shape of the bacterium and aiding in the motility. One unique feature of the B. burgdorferi PG is the chemical composition of stem peptide, which involves the atypical cross-link between Ornithine and Glycine. We identified gene bb0586 as a femX homologue in borrelial genome and hypothesize that it encodes a glycyl transferase enzyme responsible for synthesis of glycine cross-bridges, that hold together glycan strands in the peptidoglycan cell wall. Here, we predicted the structure of FemXBb, identified and characterized the substrate-binding site, and proposed a novel mechanism for substrate recognition and recruitment, involving previously uncharacterized elements of the structure. We have also determined the ability of recombinant FemXBb to add Glycine bridges to mDAP in E. coli and investigated the effect that femX knock-out can have on the B. burgdorferi. In addition, we have investigated the steps of PG biosynthesis in B. burgdorferi. The results of our research suggest the existence of a highly unusual mechanism of PG synthesis in Lyme disease spirochete, which has a potential to be used for development of targeted antibacterial therapies. / Master of Science in Life Sciences / Borrelia burgdorferi — the causative agent of Lyme borreliosis — accounts for ~500,000 infections in the United States per year. Relative to other bacteria, B. burgdorferi is highly unusual in many regards. For instance, the synthesis and composition of B. burgdorferi cell wall is extremely unique and plays a critical role in Lyme pathogenesis. The cell wall is a mesh-like structure, a sacculus, enclosing the vulnerable inside contents of a bacterial cell. It is composed of long rigid glycan strands of repeating sugars, and flexible peptide stems, interlinked by cross-bridges, holding the whole structure together. PG is an essential component for survival of the bacterial cell, protecting it from the outside stress and environmental threats, as well as defining the shape of the bacterium and aiding in the motility. B. burgdorferi PG is known to be highly atypical compared to other bacteria. One of its features is the unusual cross-link between peptides, made up of single Glycine amino acid. We identified a gene encoding a protein responsible for the addition of this amino acid during the cell wall biosynthesis. Here, we predicted the structure of this protein, its substrate-binding site, and proposed a novel mechanism for substrate recognition and recruitment. We have also expressed the borrelial protein in E. coli and confirmed its activity and the impact it has on the bacterium and investigated the effect that gene knock-out can have on the B. burgdorferi. In addition, we have investigated the steps of PG biosynthesis in B. burgdorferi. The results of our research suggest the existence of a highly unusual mechanism of PG synthesis in Lyme disease spirochete, which has a potential to be used for development of targeted antibacterial therapies.