Four commonly occurring genera of ticks in South Africa were tested for their capacity to acquire and transmit Borrelia burgdoiferi, the causative agent of Lyme disease. Attempts were made to infect rabbits with a culture of B. burgdoiferi, and tick transmission experiments were carried out using the rabbits as the host of infection. Only one rabbit was successfully infected. Histological changes associated with a B. burgdoiferi infection were noted in this rabbit, but no spirochaetes were isolated. All other host animals failed to become infected with the B. burgdoiferi. As a consequence transmission experiments with the local ticks failed. Serological surveys conducted on rodents, horses and cattle using immunofluorescent and haemagglutination tests indicated that there is evidence that Borrelia species occur widely and that there is a possibility of B. burgdoiferi occurring in South Africa. Studies conducted on ticks from suspected endemic areas revealed the presence, in Ixodes bakeri only, of a spirochaete-like organism that reacted with monoclonal antibody H5332. Shortcomings of the study are highlighted and proposals are presented to address the problem of identifying specific B. burgdoiferi infections.

No description available.

As of 2024, more than 50,000 people suffer from Lyme arthritis — a debilitating late-stage symptom of Lyme disease. Symptoms remain even after the completion of antibiotic therapy and when there is no longer any indication of an active infection. Studies have found that a portion of the bacterial cell wall from the causative agent, Borrelia burgdorferi, is a persistent antigen in Lyme arthritis patients, lingering within the synovial fluid. This antigen, peptidoglycan, is recognized by the immune system in numerous ways. Multiple publications have shown that peptidoglycan is proinflammatory and can cause arthritis when injected in vivo. The same was found to be true for B. burgdorferi peptidoglycan. Studies focused on the structure of peptidoglycan from B. burgdorferi have shown atypical differences in both glycan and peptide chemistry that likely alter immune recognition. Due to a lack of necessary enzymes and transporters B. burgdorferi are unable to recycle their peptidoglycan as they elongate and produce daughter cells. This leads to a 45% reduction of their total cell wall that is released into the environment. The work detailed below focuses on this antigen to further our knowledge as to its in vivo biodistribution pattern, half-life, and ability to induce arthritis. For these experiments B. burgdorferi peptidoglycan (pBb PG) was purified, fluorescently labeled, and tracked in vivo to study its clearance pattern and rate. Three different mouse models for Lyme arthritis were utilized in these studies and all experienced persistence of B. burgdorferi peptidoglycan in their liver for upward of 20 days. There were differences in the rate of clearance between types of mice, suggesting the involvement of host genetics. Serum collected weekly throughout this experiment showed over a log fold change in the abundance of ALT and AST levels, which indicates liver dysfunction. Proteomic analysis of the livers of mice post pBb PG injection showed altered levels of proteins important for mitochondrial function and iron homeostasis. When human PBMCs were stimulated with PG from various bacteria it was found that at 12 h pBb PG differentially expressed genes involved in energy metabolic pathways, including oxidative phosphorylation and the citric acid cycle. A subset of Lyme disease patients continue to experience symptomology even after completion of multiple rounds of antibiotics. These patients are termed to have post treatment Lyme disease syndrome and typically experience fatigue as their most common symptom. This symptom in combination with the findings of this dissertation regarding the link between pBb PG and energy metabolism warrants further investigation. Especially since this biopolymer has been found to persist in the synovial fluid of Lyme arthritis patients. Better understanding how these processes are connected could allow for the eventual development of a way to target this material for clearance, or ways to inactivate it. Both options have the potential to help alleviate the devastating symptomology experienced by patients. / Doctor of Philosophy / Lyme disease is the most common human disease originating from a nonhuman host in the United States, with the estimated number of cases ~500,000 each year. This disease is caused by the bacterium Borrelia burgdorferi, that is transmitted by the black legged tick. This disease usually causes flu-like symptoms and if left untreated can cause more severe symptomology like arthritis, carditis, and neurological symptoms. Lyme arthritis is the most common late-stage symptom of this disease. Current areas of weakness within the field include ways to diagnose this disease, the treatment options, and our understanding of how these bacteria cause the symptoms they do. Recent work has made strides in studying Lyme arthritis, suggesting a major contributing factor to be a specific component of the bacterial cell wall that continues to persist. This component is called peptidoglycan and has been found in Lyme arthritis patients even after they've finished antibiotic therapy. Studies have also shown that the structure of this cell wall component is unique in comparison to other well-known bacteria. The research conducted as a part of this dissertation aims to investigate how this bacterial peptidoglycan is able to persist within patients for so long. To study this we utilized three mouse models of Lyme disease that all develop different severities of Lyme arthritis. By isolating the peptidoglycan from B. burgdorferi and labeling it with a molecule that fluoresces, we were able to track it over time in mice. We found that in all three mouse backgrounds peptidoglycan from B. burgdorferi persists for extended periods of times in the liver. We tested peptidoglycan from other common bacteria and found that they rapidly clear the mice. This suggests that there is something about the structure of B. burgdorferi's peptidoglycan that allows it to go unnoticed by the body for so long. Since this material is persisting within the liver we wanted to test if these mice had altered liver function. We found increased serum levels of enzymes that are indicators of overall liver health, suggesting some form of dysregulation. We also measured the total abundance of proteins in the livers of these mice in comparison to healthy controls. The mice injected with B. burgdorferi peptidoglycan had changes in the level of proteins involved in energy production and iron utilization. By measuring changes in gene expression, we confirm the specificity of these results to peptidoglycan from B. burgdorferi, even when using cells isolated from humans. One of the major conundrums of Lyme disease are the patients who continue to experience symptomology even after treatment, who are referred to as having post treatment Lyme disease syndrome. The primary symptom affecting these patients is fatigue, drawing an interesting parallel to our recent studies showing that B. burgdorferi peptidoglycan seems to be impacting energy metabolism. These findings warrant further investigation into the exact way in which B. burgdorferi peptidoglycan is affecting this process, which will hopefully lead to the generation of more targeted therapies to help alleviate this symptomology.

Due to climate change, marked developments are tracked in various links of pathogen-host distribution. Markedly increased number of ectoparasites is observed in Central and Eastern Europe. Ticks are blood feeding wide group of arthropods of utmost medical, epidemiological and veterinary significance throughout the world. The ecology of ticks, the outcome of their interactions with their natural environment, is fundamental to the spatial and temporal variation in the risk of infection by tick-borne pathogens. The aim of the study was to investigate: the distribution of Ixodes ricinus ticks and their transmitted parasites prevalence in different biotopes in Lithuania; and to find out factors influencing the activity dynamics of ticks and prevalence of endoparasites. The scientific researches on ectoparasite-endoparasite system (I. ricinus-B.burgdorferi s.l., B.divergens and Ehrlichia sp.) in different biotopes in Lithuania have been carried out for the first time. Also, it was the first investigation of prevalence of ticks (according to development phases and different sexes) in different biotopes and ticks infectious by microparasites. Influence of the main factors (air temperature, precipitations) on seasonal and daily activity changes of ticks have been described. Experiments on ectoparasites and endoparasites have been employed by the procedures on molecular level, including PCR method. As the result of the study the specificity of ticks’ species has been identified... [to full text] / Vykstant klimato atšilimui yra stebimi ryškūs pokyčiai įvairiose parazitas-šeimininkas sistemos grandyse. Pastebimas ektoparazitų skaitlingumo padidėjimas Vidurio ir Rytų Europoje. Erkės yra įvairių zoonozių ir antropozių, kurias sukelia įvairūs virusai, bakterijos ir protistai, pernešėjai. Erkių platinamų ligų sukėlėjų patogeninių bakterijų (Borrelia sp., Ehrlichia sp. ir kt.) ir protistų (Babesia sp. ir kt.) tyrimus turi apimti visus ekologinius lygmenis: patogeninio organizmo, vektoriaus ir rezervuarinio šeimininko. Šio darbo tikslas – nustatyti Ixodes ricinus L. erkių ir jų pernešamų endoparazitų paplitimą skirtinguose biotopuose Lietuvoje bei išaiškinti veiksnius, turinčius įtakos erkių aktyvumui ir endoparazitų paplitimui. Lietuvoje pirmą kartą buvo atlikti ektoparazito - endoparazito sistemos (I. ricinus–B.burgdorferi s.l., B.divergens ir Ehrlichia sp.) tyrimai skirtinguose Lietuvos biotopuose. Buvo įvertintas bendras erkių (pagal vystymosi stadiją ir lytį) paplitimas skirtinguose biotopuose, jų užsikrėtimas mikroparazitais ir išanalizuoti veiksniai, lemiantys erkių aktyvumo sezoninius ir paros kitimus, gausumą ir užsikrėtimą. Ektoparazitų ir endoparazitų tyrimams buvo įdiegtas polimerazės grandininės reakcijos metodas ir identifikuotas erkių rūšinis specifiškumas, nustatyti mikroparazitai bei jų genotipai. Buvo nustatytas mikroparazitų paplitimas skirtinguose Lietuvos biotopuose ir ištirti veiksniai, galintys sąlygoti šį paplitimą. Pirmą kartą Lietuvoje buvo... [toliau žr. visą tekstą]

Diss. (sammanfattning) Linköping : Univ., 2003. / Härtill 4 uppsatser.

Thesis (Ph. D.)--West Virginia University, 2005 / Title from document title page. Document formatted into pages; contains ix, 210 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

The aim of the study was to analyze the infectious potential of the newly described species, B. americana and B. carolinensis, studied on the laboratory model mammals mice. Our goal was to analyze and compare the vectorial capacity of two different tick vectors, Amblyomma americanum and Ixodes ricinus, in acquiring and transmition of both spirochete species to the host. The results of this study confirmed that ticks A. americanum and I. ricinus are capable to maintain and transmit B. americana and B.carolinensis.We confirmed that both analysed spirochete species, B. carolinensis and B. americana, showed the potential to develop the disease in laboratory model mammal, which indirectly support the fact that both spirochete species might be concidered as the risk factors in the area where they are distributed. Our results shows that A. americanum is able to transmit both spirochete species, which increases that risk of acquiring the Lyme disease to human population in the area of distribution of A. americanum

Borrelia afzelii differential gene expression in the course of tick blood-feeding, and during chronic infection in mice was studied. Temperature effect on B. afzelii gene expression and infectivity was investigated. Infection rates of mice immunized with B. afzelii tick gut antigen at various stages of tick blood-intake were analyzed. This work was funded by the Grant Agency of the Czech Republic, Project No. 17-27393S to Radek Šíma.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-07-21T12:10:16Z No. of bitstreams: 1 2010 - Rafaella Camara Teixeira.pdf: 2127524 bytes, checksum: 2f2281ce314ac38db40bc03d628e7447 (MD5) / Made available in DSpace on 2017-07-21T12:10:16Z (GMT). No. of bitstreams: 1 2010 - Rafaella Camara Teixeira.pdf: 2127524 bytes, checksum: 2f2281ce314ac38db40bc03d628e7447 (MD5) Previous issue date: 2010-02-25 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico, CNPq, Brasil. / Cell cultures provide a simplified system of observation that can be particularly useful for studies of intracellular and epicellular microorganisms. The aim of this study was to establish in vitro embryonic cells primary culture of the tick Rhipicephalus sanguineus to cultivate the spirochete Borrelia burgdorferi american strain G39/40. The culture was established from embryonated eggs of engorged females of R. sanguineus to 12 days after the beginning of the oviposition, using the culture medium Leibovitz's L-15B supplemented with 20% of inactivated fetal calf serum, 10% of tryptose phosphate broth, 0.1% fraction V bovine albumin, 1% of glutamine and 0.1% of gentamicin antibiotic, pH 6.8. After the formation of a monolayer, the initial culture medium L-15B was removed from the tubes and replaced by Barbour-Stoenner-Kelly medium (BSK) or BSK with L-15B without antibiotics. Spirochetes previously grown in BSK were counted and inoculated into tubes, with final concentration of approximately 6.2 x 105 spirochetes/mL. B. burgdorferi from the inoculated tubes were countered when the means showed yellow color, indicative of high acidity due to the multiplication of spirochetes. On the third day after the start of primary culture of R. sanguineus embryonic cells, we observed the fixation of cell aggregates on the surface of the bottles. From these clusters, there were several cell types, such as large fibroblast-type cells and structures like vesicles and tubes. In the second week, we observed the appearance of round or flattened epithelial-type cells, and after 21 days of culture, we realized the formation of a monolayer due to the appearance of confluent cells. The L-15B medium proved to be efficient for the development of primary culture of R. sanguineus embryonic cells. There was a great multiplication of spirochetes cultivated with cultured embryonic cells when compared to the initial concentration, as well as the spirochetes grown in the absence of the tick cells, observing an increase of 100 times the number of B. burgdorferi. Seven days after inoculation, the tubes in which we used only the BSK medium, higher concentrations of B. burgdorferi were recovered when compared to the tubes where the medium BSK and Leibovitz's L-15B were used. Regardless of the culture media tested, the final concentration of B. burgdorferi of the tubes with embryonic tick cells was lower than that of seamless embryonic cells. In observation of the culture tubes on microscopy phase contrast, spirochetes were presented adhered to epithelial-type and fibroblast-type tick cells in an epicelular way and with great motility. R. sanguineus embryonic cells grown in BSK medium, with or without B. burgdorferi inoculation, stopped its propagation, showed membrane degeneration and many of them broke away from the surface of the bottle. The cells grown in BSK and L- 15B continued to multiply, many were still intact and attached to the bottle, with the presence of tissues in development, with fewer degenerated and floating cells than those cultivated in BSK. The spirochete B. burgdorferi strain G39/40, adhered, grew, multiplied and showed great motility in cultures of embryonic cells of R. sanguineus tick, using BSK and Leibovitz?s L-15B media. / As culturas celulares oferecem um simplificado sistema de observa??o que pode ser particularmente ?til para estudos de microrganismos intracelulares e epicelulares. O objetivo deste estudo foi estabelecer cultura prim?ria in vitro de c?lulas embrion?rias do carrapato Rhipicephalus sanguineus para cultivo da espiroqueta Borrelia burgdorferi, cepa americana G39/40. A cultura foi estabelecida a partir de ovos embrionados de f?meas ingurgitadas de R. sanguineus com 12 dias ap?s o ?nicio da postura, utilizando o meio de cultivo Leibovitz?s L- 15B, suplementado com 20% de soro fetal bovino inativado, 10% de caldo triptose fosfato, 0,1% fra??o V de albumina bovina, 1% de glutamina e 0,1% de antibi?tico gentamicina, pH 6,8. Com a forma??o de uma monocamada celular, o meio de cultura inicial L-15B foi retirado dos tubos e trocado por meio Barbour-Stoenner-Kelly (BSK) ou BSK com L-15B sem antibi?tico. As espiroquetas previamente cultivadas em BSK foram contadas e inoculadas nos tubos, apresentando concentra??o final de aproximadamente 6,2 x 105 espiroquetas/mL. A contagem de B. burgdorferi dos tubos inoculados foi realizada quando o meio apresentou colora??o amarela, indicativa de elevada acidez devido ? multiplica??o das espiroquetas. No terceiro dia ap?s o in?cio da cultura prim?ria de c?lulas embrion?rias de R. sanguineus, foi poss?vel observar a fixa??o de agregados celulares na superf?cie dos frascos. A partir destes agregados, surgiram diversos tipos celulares, como grandes c?lulas fibroblast?ides e estruturas semelhantes a ves?culas e tubos. Na segunda semana, foi observado o aparecimento das c?lulas epiteli?ides ou redondas e, com 21 dias de cultivo, visualizou-se a forma??o de uma monocamada celular devido ao aspecto confluente das c?lulas. O meio de cultivo L-15B demonstrou ser eficiente para o desenvolvimento da cultura prim?ria de c?lulas embrion?rias de R. sanguineus. Houve grande multiplica??o das espiroquetas cultivadas com c?lulas embrion?rias quando comparada ? concentra??o inicial, assim como das espiroquetas cultivadas na aus?ncia das c?lulas de carrapato, observando-se um aumento em 100 vezes do n?mero de B. burgdorferi. Sete dias ap?s a inocula??o, foram recuperadas maiores concentra??es de B. burgdorferi nos tubos onde se utilizou somente o meio BSK, do que nos tubos onde foi utilizado BSK juntamente com Leibovitz?s L-15B. Independente dos meios de cultivo testados, a concentra??o final de B. burgdorferi dos tubos com c?lulas embrion?rias de carrapato foi menor do que a dos tubos sem c?lulas embrion?rias. Na observa??o dos tubos de cultivo ? microscopia de contraste de fase, as espiroquetas apresentaram-se aderidas ?s c?lulas de carrapato epiteli?ides e fibroblast?ides de maneira epicelular e com grande motilidade. As c?lulas embrion?rias de R. sanguineus cultivadas em meio BSK, com ou sem in?culo de B. burgdorferi, pararam sua multiplica??o, apresentaram degenera??o na membrana e muitas desprenderam-se da superf?cie do frasco. As c?lulas cultivadas em meio BSK e L-15B continuaram a se multiplicar, muitas ainda estavam ?ntegras e aderidas ao frasco, com presen?a de tecidos em desenvolvimento, com menos c?lulas degeneradas e flutuantes que as cultivadas somente em BSK. A espiroqueta B. burgdorferi, cepa G39/40, aderiu, cresceu, multiplicou e apresentou grande motilidade nos cultivos com c?lulas embrion?rias do carrapato R. sanguineus, utilizando meios BSK e Leibovitz?s L-15B.

Die Gattung Borrelia gehört zur Abteilung der Spirochäten, einem alten Zweig der Bakteriendomäne, der nur entfernt mit Gram-negativen Bakterien verwandt ist. Sämtliche Arten dieser Gattung sind obligate Parasiten. Borrelien können in die Erreger zweier humaner Krankheiten eingeteilt werden: die Lyme-Borreliose und das Rückfallfieber. Borrelien besitzen mit 0.91 Mb ein sehr kleines Chromosom und sind daher in ihren metabolischen Fähigkeiten eingeschränkt. Folglich ist das Überleben sämtlicher Borrelienarten absolut abhängig von Nährstoffen, die von ihren Wirten bereitgestellt werden. Der Transport dieser Nährstoffe und anderer Moleküle über die äußere Membran wird durch porenformende Proteine, so genannte Porine ermöglicht. Porine sind wassergefüllte Kanäle, die in zwei Klassen unterteilt werden können: allgemeine Diffusionsporen und substratspezifische Porine. Aus dem Lyme-Borreliose Erreger Borrelia burgdorferi wurden bisher drei mutmaßliche Porine charakterisiert und beschrieben: P13, Oms28 und P66. Demgegenüber sind die Kenntnisse über Porine in Rückfallfieberarten rudimentär und es wurde bisher noch kein einziges Porin für Vertreter dieser Krankheit identifiziert. Unter Berücksichtigung dieses Hintergrunds war die allgemeine Zielsetzung dieser Arbeit, einen Einblick in die Porinzusammensetzung von sowohl Lyme Borreliose- als auch Rückfallfieber-Spirochäten zu erlangen. Dieses Ziel konnte erreicht werden, indem Porine aus den Außenmembranen von Borrelien isoliert und identifiziert wurden und anschließend biophysikalisch in künstlichen Lipidmembranen charakterisiert wurden. Ein Kapitel dieser Arbeit beschreibt die Identifizierung und Charakterisierung des ersten Porins aus Rückfallfiebererregern. Das porenformende Protein wurde aus den Außenmembranen von Borrelia duttonii, Borrelia hermsii und Borrelia recurrentis isoliert und Oms38 genannt, für „outer membrane-spanning protein of 38 kDa“. Die biophysikalische Charakterisierung mit der „black lipid bilayer“ Methode zeigte, dass Oms38 kleine, wassergefüllte Kanäle mit einer Einzelkanalleitfähigkeit von 80 pS in 1 M KCl bildet. Diese Kanäle sind nicht spannungsabhängig und leicht selektiv für Anionen mit einem Permeabilitätsverhältnis von Kationen zu Anionen von 0,41 in KCl. Ein homologes Protein zu Oms38 wurde in den Lyme Borreliose Erregern Borrelia burgdorferi, Borrelia garinii und Borrelia afzelii identifiziert. Das porenformende Protein dieser Arten weist eine hohe Sequenzhomologie zu Oms38 auf und zeigt ähnliche biophysikalische Eigenschaften, das heißt es formt Poren von 50 pS in 1 M KCl. Durch Titrationsexperimente konnte gezeigt werden, dass die Pore teilweise durch Dicarboxylate blockiert werden kann. Eine Auswertung dieser Versuche legte nahe, dass dieses Protein keine allgemeine Diffusionspore darstellt, sondern einen Kanal mit einer spezifischen Bindestelle für diese Komponenten. Daher wurde dieses Porin DipA genannt, was für „dicarboxylate-specific porin A“ steht. In einer anderen Versuchsreihe wurde gezeigt, dass das Porin P66 sowohl in Lyme Borreliose Erregern als auch in Rückfallfieberarten vorhanden ist. Hierfür wurden die Außenmembranen der Lyme Borreliose Erreger Borrelia burgdorferi, Borrelia afzelii und Borrelia garinii und der Rückfallfieberarten Borrelia duttonii, Borrelia recurrentis und Borrelia hermsii genauer untersucht. Mit Ausnahme des P66 Homologs von Borrelia hermsii rekonstituierten P66 Proteine aus allen Arten sehr aktiv in künstliche Membranen und formten Poren zwischen 9 und 11 nS in 1 M KCl. Die biophysikalischen Eigenschaften der Homologe wurden in Experimenten mit „black lipid bilayer“ Membranen ausführlich verglichen. Des Weiteren wurden Porendurchmesser und Konstitution des Borrelia burgdorferi Porins P66 genau untersucht. Hierfür wurde die P66 Einzelkanalleitfähigkeit in Anwesenheit von verschiedenen Nichtelektrolyten in künstlichen Lipidmembranen analysiert. Der effektive Durchmesser des P66 Wasserlumens wurde auf ~1.9 nm bestimmt. Darüber hinaus konnte P66 mit bestimmten Nichtelektrolyten wie PEG 400, PEG 600 und Maltohexaose blockiert werden. Weitere Blockierungsexperimente auf Einzelkanalebene deckten sieben Unterzustände von P66 auf, die auf ein P66 Heptamer schließen ließen. Dieser heptamere Charakter konnte durch Blue native PAGE Analysen bestätigt werden. Zusammenfassend beschreibt diese Dissertation detaillierte biochemische und biophysikalische Untersuchungen von Porinen aus sowohl Lyme Borreliose- als auch Rückfallfieber-Borrelien. Erkenntnisse aus dieser Arbeit bringen das Verstehen der Nährstoffaufnahme über Außenmembranen dieser streng wirtsabhängigen, pathogenen Spirochäten einen großen Schritt vorwärts. Ein fundiertes Wissen über oberflächenexponierte Proteine wie Porine ist Vorraussetzung für die Herstellung erfolgreicher Impfstoffe und Therapeutika gegen die von Borrelien verursachten Krankheiten. / The genus Borrelia belongs to the spirochete phylum, an ancient evolutionary branch of the domain bacteria that is only afar related to Gram-negative bacteria. Borreliae can be subdivided into the agents of the two borrelian-caused human diseases, Lyme disease and relapsing fever. Both disease patterns are closely related to the peculiar biology of Borrelia species and exhibit a wide spectrum of diverse clinical manifestations. Due to the small 0.91 Mb chromosome, borreliae have a lack of biosynthetic capacity. Thus, all Borrelia species are highly dependent on nutrients provided by their hosts. The transport of nutrients and other molecules across the outer membrane is enabled by pore-forming proteins, so-called porins. Porins are water-filled channels and can be subdivided into two different classes, general diffusion pores and substrate-specific porins. In terms of the Lyme disease agent Borrelia burgdorferi, three putative porins were characterized in previous studies: P13, Oms28 and P66. In contrast to Lyme disease species, the porin knowledge of relapsing fever Borrelia is low, which means that not any porin has actually been described for representatives of these agents. Thus, the general aim of this thesis was to provide insight into the porin content of both, Lyme disease and relapsing fever spirochetes. This aim could be achieved by isolating and identifying porins from Borrelia outer membranes and by biophysically characterizing them in artificial lipid membranes. In one chapter of this study, the first identification and characterization of a relapsing fever porin is presented. The pore-forming protein was isolated from outer membranes of Borrelia duttonii, Borrelia hermsii and Borrelia recurrentis and designated Oms38, for “outer membrane-spanning protein of 38 kDa”. Biophysical characterization of Oms38 was achieved by using the black lipid bilayer method and demonstrated that Oms38 forms small, water-filled channels with a single-channel conductance of 80 pS in 1 M KCl. The Oms38 channel did not exhibit voltage-dependent closure and is slightly selective for anions with a permeability ratio of cations over anions of 0.41 in KCl. Subsequently, a protein homologous to Oms38 was identified in the Lyme disease agents Borrelia burgdorferi, Borrelia garinii and Borrelia afzelii. The pore-forming protein of these species exhibits high sequence homology to Oms38 and similar biophysical properties, i.e. it forms pores of 50 pS in 1 M KCl. Interestingly, titration experiments revealed that this pore could be partly blocked by dicarboxylic anions, which means that this protein does not form a general diffusion pore but a channel with a binding-site specific for those compounds. Consequently, this porin was termed DipA, for “dicarboxylate-specific porin A”. In another set of experiments, it was shown that the porin P66 is present in both Lyme disease and relapsing fever species. Therefor, the outer membranes of the Lyme disease species Borrelia burgdorferi, Borrelia afzelii, Borrelia garinii and the relapsing fever species Borrelia duttonii, Borrelia recurrentis and Borrelia hermsii were closer investigated. Except of the P66 homologue of Borrelia hermsii P66 of all species was highly active in artificial lipid membranes, forming pores with huge single-channel conductances between 9 and 11 nS in 1 M KCl. Moreover, the channel diameter and the constitution of Borrelia burgdorferi P66 were investigated in detail. Therefor, the P66 single-channel conductance in the presence of different nonelectrolytes with known hydrodynamic radii was analyzed in black lipid bilayers. The effective diameter of the P66 channel lumen was determined to be ~1.9 nm. Furthermore, as derived from multi-channel experiments the P66-induced membrane conductance could be blocked by certain nonelectrolytes, such as PEG 400, PEG 600 and maltohexaose. Additional blocking experiments on the single-channel level revealed seven subconducting states and indicated a heptameric constitution of the P66 channel. This indication could be confirmed by Blue native PAGE analysis which demonstrated that P66 units form a complex with a corresponding mass of approximately 440 kDa. Taking together, this thesis describes detailed biochemical and biophysical investigations of both Lyme disease and relapsing fever Borrelia porins and represents an important step forward in understanding the outer membrane pathways for nutrient uptake of these strictly host-dependent, pathogenic spirochetes. Furthermore, it provides some knowledge of the outer-membrane protein composition of Borrelia spirochetes. A profound knowledge of surface-exposed proteins, such as porins, is one precondition for the production of a successful vaccine and the drug design against the two borrelian-caused diseases.