The critical role of the linear plasmid lp36 in the infectious cycle of Borrelia burgdorferi.

Borrelia burgdorferi, the aetiological agent of Lyme disease, follows a life cycle that involves passage between the tick vector and the mammalian host. To investigate the role of the 36 kb linear plasmid, lp36 (also designated the B. burgdorferi K plasmid), in the infectious cycle of B.

Borrelia burgdorferi OspC protein required exclusively in a crucial early stage of mammalian infection.

This study demonstrates a strict temporal requirement for a virulence determinant of the Lyme disease spirochete Borrelia burgdorferi during a unique point in its natural infection cycle, which alternates between ticks and small mammals. OspC is a major surface protein produced by B. burgdorferi when infected ticks feed but whose synthesis decreases after transmission to a mammalian host.

Delineating the requirement for the Borrelia burgdorferi virulence factor OspC in the mammalian host.

We previously demonstrated that outer surface protein C (OspC) of Borrelia burgdorferi is essential for establishing mammalian infection. However, the role of OspC in mammalian infection is unknown. Here, we report experiments designed to distinguish between two models of OspC function in the mammalian host: (i) OspC fulfills an essential physiological role for growth and host adaptation or (ii) OspC provides a protective role for evasion of components of the innate immune response.

Defining plasmids required by Borrelia burgdorferi for colonization of tick vector Ixodes scapularis (Acari: Ixodidae).

Maintenance in nature of Borrelia burgdorferi, the pathogenic bacterium that causes Lyme disease, requires transmission through an infectious cycle that includes a tick vector and a mammalian host. The genetic requirements for persistence in these disparate environments have not been well defined. B.

Borrelia burgdorferi sigma54 is required for mammalian infection and vector transmission but not for tick colonization.

Previous studies have shown that a sigma54-sigma(S) cascade regulates the expression of a few key lipoproteins in Borrelia burgdorferi, the agent of Lyme disease. Here, we demonstrate that these sigma factors, both together and independently, regulate a much more extensive number of genes and cellular processes. Microarray analyses of sigma54 and sigma(S) mutant strains identified 305 genes regulated by sigma54 and 145 regulated by sigma(S), whereas the sigma54-sigma(S) regulatory cascade appears to control 48 genes in B.

The plasmids of Borrelia burgdorferi: essential genetic elements of a pathogen.

The spirochete Borrelia burgdorferi, the causative agent of Lyme disease, has an unusual genome comprised of a linear chromosome and the largest plasmid complement of any characterized bacterium. Certain plasmid-encoded elements are required for virulence and viability, both in vitro and in vivo. The genetic tools to manipulate B.

Experimental assessment of the roles of linear plasmids lp25 and lp28-1 of Borrelia burgdorferi throughout the infectious cycle.

Borrelia burgdorferi, which causes Lyme disease in humans, has an unusual genome composed of a linear chromosome and up to 21 extrachromosomal elements. Experimental data suggest that two of these elements, linear plasmids lp25 and lp28-1, play essential roles for infectivity in mice. In this study, we prove the essential natures of these two plasmids by selectively displacing lp25 or lp28-1 in an infectious wild-type clone with incompatible shuttle vectors derived from the native plasmids, rendering the respective transformants noninfectious to mice.

Infectious cycle analysis of a Borrelia burgdorferi mutant defective in transport of chitobiose, a tick cuticle component.

Chitobiose is the dimer subunit of chitin, a component of tick cuticle and peritrophic matrix, which is not found in mammals. The Borrelia burgdorferi chbC gene is required for the use of chitobiose as a source of the essential nutrient N-acetyl glucosamine during growth in vitro. In order to investigate the role of chitobiose transport in the infectious cycle, we constructed isogenic chbC mutant and wild-type strains in an infectious B.

Outer-surface protein C of the Lyme disease spirochete: a protein induced in ticks for infection of mammals.

Environmentally responsive synthesis of surface proteins represents a hallmark of the infectious cycle of the Lyme disease agent, Borrelia burgdorferi. Here we created and analyzed a B. burgdorferi mutant lacking outer-surface protein C (OspC), an abundant Osp that spirochetes normally synthesize in the tick vector during the blood meal and down-regulate after transmission to the mammal.

Plasmid stability during in vitro propagation of Borrelia burgdorferi assessed at a clonal level.

Borrelia burgdorferi causes Lyme disease in humans. The genome of the sequenced type strain B31 MI consists of a linear chromosome, 12 linear plasmids, and 9 circular plasmids. Previous studies by other investigators indicated that some of these plasmids are essential for the survival of the spirochetes in vivo but not in vitro.

Clonal polymorphism of Borrelia burgdorferi strain B31 MI: implications for mutagenesis in an infectious strain background.

A major obstacle to studying the functions of particular gene products in the mouse-tick infectious cycle of Borrelia burgdorferi has been an inability to knock out genes in pathogenic strains. Here, we investigated conditions for site-directed mutagenesis in B31 MI, the low-passage-number, infectious B. burgdorferi strain whose genome was sequenced.