Reproduction and metabolism at -10°C of bacteria isolated from Siberian permafrost

We report the isolation and properties of several species of bacteria from Siberian permafrost. Half of the isolates were spore-forming bacteria unable to grow or metabolize at subzero temperatures. Other Gram-positive isolates metabolized, but never exhibited any growth at -10°C. One Gram-negative isolate metabolized and grew at -10°C, with a measured doubling time of 39 days. Metabolic studies of several isolates suggested that as temperature decreased below +4°C, the partitioning of energy changes with much more energy being used for cell maintenance as the temperature decreases. In addition, cells grown at -10°C exhibited major morphological changes at the ultrastructural level.