Stress-shock Response of a Methylotrophic Bacterium Methylovorus sp. strain SS1 DSM 11726

Methylovorus sp. strain SS1 DSM 11726 was found to grow continuously when it was transferred from 30°C to 40°C and 43°C. A shift in growth temperature from 30°C to 45°C, 47°C and 50°C reduced the viability of the cell population by more than 10², 10³ and 10⁵ folds, respectively, after l h cultivation. Cells transferred to 47°C and 50°C after preincubation for 15 min at 43°C, however, exhibited 10-fold increase in viability. It was found that incubation for 15 min at 40°C of Methylovorus sp. strain SS1 grown at 30°C was sufficient to accelerate the synthesis of a specific subset of proteins. The major heat shock proteins had apparent molecular masses of 90,70, 66, 60, and 58 kDa. The 60 and 58 kDa proteins were found to cross-react with the antiserum raised against GroEL protein. The heat shock response persisted for over 1 h. The shock proteins were stable for 90 min in the cell. Exposure of the cells to methanol induced proteins identical to the heat shock proteins. Addition of ethanol induced a unique protein with a molecular mass of about 40 kDa in addition to the heat- induced proteins. The proteins induced in paraquat-treated cells were different from the heat shock proteins, except the 70 and 60 kDa proteins.