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Thermoregulation of protein synthesis in Borrelia burgdorferi

Borrelia burgdorferi, the etiological agent of Lyme disease, infects humans via the bite of a tick. The microbe survives in at least two vastly different environments: an arthropod vector and a warm-blooded host. We examined protein synthesis in B. burgdorferi B31 in response to sudden heat stress, which is similar to that which occurs during the transmission from vector to host. Proteins synthesized after shifts from 28 degrees C to higher temperatures and in pulse-chase experiments were labeled with 3H-labeled amino acids for 4 h and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. The synthesis of four proteins we designated as heat stress proteins (HSPs) was increased by shifts to higher temperatures (HSP-1, 75 kilodaltons [kDa]; HSP-2, 42 kDa; HSP-3, 39 kDa; and HSP-4, 27 kDa); and the amount of one protein we designated as heat-labile protein 1 (29.5 kDa) was decreased at higher temperatures. At 37 to 40 degrees C, the major heat stress protein, HSP-1, represented 14 to 18% of the total cell protein compared with 1 to 2% of the total cell protein at 28 degrees C. HSP-1 was stable during a 4-h chase at either 40 or 28 degrees C. Demonstration of similar HSPs in low-passage, pathogenic strains of B. burgdorferi suggests that the heat stress response may be common among B. burgdorferi strains and may play a role in Lyme disease.