The uptake of glucose by a thermophilic Bacillus sp

A phosphoenolpyruvate-dependent phosphotransferase that effects the uptake and phosphorylation of glucose and of methyl α-glucoside is inducibly formed when glucose is added to cultures of Bacillus stearothermophilus, var. non-diastaticus, that are growing at 55 °C on media containing acetate or succinate, but not when growing on fructose, as carbon source. This phosphotransferase is no less stable in intact cells than are other proteins: it is diluted out, but not preferentially destroyed, when glucose-grown inocula grow on fructose. Suspensions of non-growing cells kept at 55 °C lose half their glucose phosphotransferase activity in 2 to 3 h; this is similar to the rate at which this activity is lost from suspensions of mesophilic bacilli kept at 35 °C, which is close to their optimal growth temperature. However, in absolute terms, the glucose phosphotransferase activity of mesophiles is much more sensitive to heat denaturation than that of thermophiles.