Abstract

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 10^2 , 10^3 and 10^5 folds, respectively, after 1 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.

• Keywords: Methylovorus sp. strain SS1; stress response; heat shock proteins