Acquired thermotolerance and heat shock proteins in thermophiles from the three phylogenetic domains

Thermophilic organisms from each of the three phylogenetic domains (Bacteria, Archaea, and Eucarya) acquired thermotolerance after heat shock. Bacillus caldolyticus grown at 60°C and heat shocked at 69°C for 10 min showed thermotolerance at 74°C, Sulfolobus shibatae grown at 70°C and heat shocked at 88°C for 60 min showed thermotolerance at 95°C, and Thermomyces lanuginosus grown at 50°C and heat shocked at 55°C for 60 min showed thermotolerance at 58°C. Determinations of protein synthesis during heat shock revealed differences in the dominant heat shock proteins for each species. For B. caldolyticus, a 70-kDa protein dominated while for S. shibatae, a 55-kDa protein dominated and for T. lanuginosus, 31- to 33-kDa proteins dominated. Reagents that disrupted normal protein synthesis during heat shock prevented the enhanced thermotolerance.