Zent.bl. Bakteriol. 288, 451-455 (1998) © Gustav Fischer Verlag Zentralblatt fUr Growth Parameters of Borrelia burgdorferi sensu stricto at Various Temperatures M. Heroldova}, M. Nemec}, and Z. Hubalek 2 1 Department of Microbiology, Faculty of Science, Masaryk University, Brno 2 Laboratory of Medical Zoology, Institute of Vertebrate Biology, Academy of Scien- ces of the Czech Republic, Brno Received June 15, 1998 . Revision received August 10, 1998 . Accepted September 10, 1998 Summary Growth of Borrelia burgdorferi sensu stricto (prototype strain B-31) was studied in Barbour-Stoenner-Kelly BSK-H liquid medium, supplemented with 4.5 % rabbit serum and antibiotics (phosphomycin, rifampicin), at various temperatures to early station- ary growth phase. The number of cells was determined by darkfield microscopy. In the range of cultivation temperatures of 25°C to 37 °C, generation time was between 8.26 and 12.36 h (the shortest one at 33 0q, and the specific growth rate between 0.056 and 0.083 h- 1 (the highest one at 33 0q. The optimum growth temperature for B. burg- dorferi was 33°C, although good growth was also observed at 28 °C, 30°C, 35 °C and 37°C. The strain grew well but slowly at the temperature of 25°C, whereas no growth was observed at 20 0c. Introduction The causative agent of Lyme disease, Borrelia burgdorferi sensu lato (s.1.), is a spirochete "shuttling" between two organisms: arthropod vector (ixodid tick) and homeotherm vertebrate host. This life cycle requires the ability of the microorganism to multiply at different temperatures and environments: a) at ambient temperature (in the vector tick); b) at 32-3rc (temperature of body surface of the vertebrate host); c) at 37-41 °c (temperature of internal organs of the vertebrate host - mam- mal or bird). The knowledge about growth abilities of B. burgdorferi and its growth pa- rameters in vitro are limited because of its generally slow growth and high cul-