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Keywords:

  • Rhodospirillum centenum;
  • Photosynthesis;
  • Thermotolerance;
  • Cysts

Abstract

Rhodospirillum centenum nov. sp., isolated from Thermopolis Hot Springs (Wyoming), is a thermotolerant non-sulfur purple photosynthetic bacterium that forms desiccation- and heat-resistant cysts under certain nutritional conditions. Phototrophic growth rate is optimal over the temperature range ca. 39–45°C, and the maximum growth temperature is ca. 47°C. The bacterium requires biotin and vitamin B12, and grows readily in synthetic media. Growth rate, however, is markedly stimulated by unknown organic compounds in Soytone and similar preparations from soybeans. Dried cysts of R. centenum show high resistance to heating at 55–75°C for 48 h, suggesting that cysts provide a mechanism for survival and species dispersal in natural thermal environments.