Effect of water activity on the mechanical glass transition and dynamical transition of bacteria

Sogabe, Tomochika*; Nakagawa, Hiroshi   ; Yamada, Takeshi*; Koseki, Shigenobu*; Kawai, Kiyoshi*

The purpose of this study was to clarify the glass transition behavior of bacteria () as a function of water activity (). Mechanical relaxation was investigated at 298 K, and the mechanical ( at which mechanical glass transition occurs at 298 K) was determined to be 0.667. Temperature-dependency of mean square displacement was investigated by inelastic neutron scattering. From the linear fitting, two dynamical transition temperatures (low and high-) were determined. There was a minor effect of on the low- except for the anhydrous sample. The high- largely increased with the decrease in . The dynamical determined by high- (0.688) was slightly higher than the mechanical because of the difference in the measurement time-scale. The high- was converted to the glass transition temperature (), and anhydrous was estimated to be 411 K. Bacterial inactive-active transition was discussed according to the glass transition behavior.