Low-temperature growth of Shewanella oneidensis MR-1.

Shewanella oneidensis MR-1 is a mesophilic bacterium with a maximum growth temperature of approximately 35 degrees C but the ability to grow over a wide range of temperatures, including temperatures near zero. At room temperature ( approximately 22 degrees C) MR-1 grows with a doubling time of about 40 min, but when moved from 22 degrees C to 3 degrees C, MR-1 cells display a very long lag phase of more than 100 h followed by very slow growth, with a doubling time of approximately 67 h. In comparison to cells grown at 22 degrees C, the cold-grown cells formed long, motile filaments, showed many spheroplast-like structures, produced an array of proteins not seen at higher temperature, and synthesized a different pattern of cellular lipids. Frequent pilus-like structures were observed during the transition from 3 to 22 degrees C.