Culturability and survival of an extreme thermophile from deep-sea hydrothermal vents

The culturability of a strictly anaerabic, extremely thermophilic archaeon, Thermococcus peptonophilus (optimal growth temperature: 85 degrees C), was studied during survival stages at various temperatures (98, 85, 70, and 4 degrees C). Total cell number (determined by DAPI staining), active cells (rhodaminc-stained cells), and culturable cells (using most-probable-number) were counted over time. The number of culturable cells decreased under each condition tested. The total number-of cells significantly decreased only al temperatures close to the maximum for growth (98 degrees C); at this temperature, the cells spontaneously lysed. Our results suggested that survival at 4 degrees C in oxygenated waters might be a mechanism for the dispersion of extreme thermophiles in the ocean. In addition, we proved the existence of T. peptonophilus cells in several physiological states: culturable cells, active non-culturable cells, inactive non-culturable cells, and dead cells. Cell death was caused by cellular lysis.