Date of Graduation
School of Medicine
Microbiology, Immunology, and Cell Biology
Nyles W. Charon.
Spirochetes are unique bacteria that cause a variety of diseases. Motility, provided by periplasmic flagella (PFs), is a virulence factor for spirochetes. This work focuses on PFs from Borrelia burgdorferi and Brachyspira hyodysenteriae. PFs consist of three main parts: basal body, hook, and filament. Monoclonal antibodies were developed to attempt identification of individual FlaB filament proteins in B. hyodysenteriae .;The PF filament of B. burgdorferi consists of a major flagellin, FlaB, and a minor flagellin, FlaA. FlaB constitutes 10-14%, whereas FlaA contributes less than 0.5%, of total cellular protein. Although these flagellins co-precipitate, the location of FlaA on a PF is unknown. FlaA accumulates at only 13% of wild type levels in the flaB null mutant, MC-1. Because mRNA levels are not negatively altered, FlaA regulation occurs at a posttranscriptional level. As FlaA is degraded over time, protein turnover may be a mechanism responsible for reduced FlaA accumulation in MC-1.;The flagellar hook has structural and regulatory roles in many bacteria. The PF hook gene, flgE, is required for motility, wave-like cell morphology, and PF synthesis in B. burgdorferi. The flgE null mutant, SC-1, has markedly reduced levels of filament proteins FlaB and FlaA. Because flaB and flaA transcripts are not negatively altered, filament protein synthesis is regulated at a posttranscriptional level. As seen in MC-1, FlaA is degraded over time in SC-1. Conversely, FlaB is stable indicating that protein turnover is not a significant mechanism for maintaining reduced FlaB accumulation in SC-1.;In addition to a loss of FlgE in SC-1, a series of high molecular weight bands reactive to hook antisera was lost. This "ladder" was present in wild type strains B31 and N40, and also in MC-1 cells, all of which presumably assemble the PF hook. The ladder is absent in SC-1 and fliF null basal body mutants in which the PF hook cannot assemble. Furthermore, the ladder is present in purified PFs and in isolated hook-basal body complexes from B31 PFs. The ladder suggests that these bands are FlgE aggregates that are strongly associated, perhaps by cross-linking. The nature of FlgE protein association is currently unknown.
Sal, Melanie S., "Periplasmic flagella of the spirochetes Borrelia burgdorferi and Brachyspira hyodysenteriae" (2005). Graduate Theses, Dissertations, and Problem Reports. 2280.