groEL expression in gyrB mutants of Borrelia burgdorferi

GroEL protein and groEL mRNA transcript were up-regulated in gyrB mutants of Borrelia burgdorferi, a causative agent of Lyme disease. Furthermore, the protein and transcript levels in gyrB mutants were greater than those in experimentally heat-shocked cultures of wild-type B. burgdorferi. Circular DNA in the gyrB mutants was more relaxed than in wild-type cells, although groEL is on the linear chromosome of B. burgdorferi. To our knowledge, this is the first evidence, albeit indirect, for the effect of DNA topology on gene expression from a linear DNA molecule in a bacterium. Lyme disease is a multisystem disorder caused by the spiro-chete Borrelia burgdorferi (4, 24). Pathology to host tissues may be due in part to an autoimmune response to B. burgdorferi heat shock proteins (HSPs) (13). HSPs are synthesized when cells are exposed to elevated temperatures or to a variety of other stresses (11). Some HSPs have been shown to act as chaperones for the assembly of complex and oligomeric pro-teins (2, 8). The major HSP of 72 kDa, the DnaK homolog (1, 25), is immunoreactive, and antibodies to DnaK are com