Lyme disease is the most prevalent arthropod borne, emerging infectious disease. The disease is caused by the spirochete Borrelia burgdorferi, which is transmitted to humans via infected Ixodes ticks (Ixodes scapularis; commonly known as deer ticks). Lyme disease is a multiple-systemic disorder with various clinical symptoms including: erythema migrans rash, arthritis, cardiac, musculoskeletal and neurological manifestations. In the United States, approximately 60% of untreated patients develop Lyme arthritis, and more than 10% of these patients become treatment-resistant for unknown reasons. In addition, 4-10% of the untreated Lyme patients develop carditis. Currently, no vaccines are available to prevent Lyme disease.

When a tick feeds, the spirochetes migrate from the tick midgut to its salivary glands and then into the mammalian host. Borrelia burgdorferi is highly invasive: After deposition in the skin by a tick bite, spirochetes traverse the intracellular matrix, penetrate the vascular endothelial cell lining, and are disseminated to large joints, ears, heart and other tissues. However, the mechanisms involved in this invasive process, and how the organisms migrate from the tick midgut to the salivary glands, are unknown.

 

Borrelia burgdorferi has a wave-like morphology and unique means of motility. The organelles for motility, periplasmic flagella, are located in the periplasmic space within the outer membrane sheath and cell cylinder. These spirochetes are able to swim in highly viscous, gel-like environments such as joints, connective tissues and brain where most externally-flagellated bacteria move slowly or stop swimming. Periplasmic flagella are essential for both motility and morphology of Borrelia burgdorferi, as mutations in the gene encoding the major periplasmic flagellar protein results in cells that are rod-shaped and non motile.

Bacterial pathogens are highly adapted, with survival strategies that require multiplication and living in hosts. Chemotaxis two-component phosphorelay systems are fundamental to many adaptive responses and are often essential for virulence in host organisms. While motility and chemotaxis are critical for many pathogenic organisms to colonize and/or cause disease, the role of these processes in Borrelia burgdorferi-mediated pathogenesis has not been determined.

 

One of our immediate goals is to determine the extent to which motility and chemotaxis in Borrelia burgdorferi is involved in transmission and disease progression. Our long term goal is to identify a molecule or a pathway (e.g., chemotaxis signal transduction pathway) in the organism for which a novel pharmacological agent can be developed to better treat or prevent the multi-systemic Lyme disease.

M. Sal, C. Li, M. A. Motaleb, and N. W. Charon, 2008. Borrelia burgdorferi uniquely regulates its motility genes and has an intricate flagellar hook basal body structure. Journal of Bacteriology 190: 1912-21.

 

 

M.  A. Motaleb, M. R. Miller, R. G. Bakker, C. Li, and N. W. Charon, 2007. Isolation and characterization of chemotaxis mutants of the Lyme disease spirochete Borrelia burgdorferi using allelic exchange mutagenesis, flow cytometry, and cell tracking.  Methods in Enzymology 422: 421-437.

 

M. A. Motaleb, M. R. Miller, C. Li, and N. W. Charon, 2007.  Phosphorylation assays of chemotaxis two-component system proteins in Borrelia burgdorferi. Methods in Enzymology 422: 438-447.

 

N. W. Charon, M. Sal, M. R. Miller, R. G. Bakker, C. Li, and M. A. Motaleb, 2006. Motility gene regulation and chemotaxis in Borrelia burgdorferi.  Molecular Biology of Spirochetes. IOS press, The Netherlands (Book chapter) Vol 373:42-49.

 

M. A. Motaleb, M. R. Miller, C. Li, R. G. Bakker, S. F. Goldstein, R. E. Silversmith, R. B. Bourret, and N. W. Charon, 2005. CheX is a phosphorylated CheY phosphatase essential for Borrelia burgdorferi chemotaxis. Journal of Bacteriology 23:7963-7969.

 

M.  A. Motaleb, M. S. Sal and N. W. Charon, 2004. The decrease in FlaA observed in a flaB mutant of Borrelia burgdorferi occurs posttranscriptionally. Journal of Bacteriology 186:3703-11.

 

C. Li, R. G. Bakker, M. A. Motaleb, M. L. Sartakova, F. C. Cabello and N. W. Charon, 2002.Asymmetrical flagellar rotation in Borrelia burgdorferi nonchemotactic mutants. Proc. Natl. Acad. Sci. USA99:6169-74.

 

M. Sartakova, E. Y. Dobrikova, M. A. Motaleb, H. P. Godfrey, N. W. Charon and F. C. Cabello, 2001. Complementation of a nonmotile flaB mutant of Borrelia burgdorferi by chromosomal integration of a plasmid containing a wild type flaB allele. Journal of Bacteriology 183: 6558-64.

 

M. A. Motaleb, L. Corum, J. L. Bono, A. F. Elias, P. Rosa, D. S. Samuels, N. W. Charon, 2000.  Borrelia burgdorferi periplasmic flagella have both skeletal and motility functions.  Proc. Natl. Acad. Sci. USA, 97: 10899-904.