Microbacterium thermosphactum was grown at 5 degrees C in glucose-limited continuous cultures. The end products of glucose metabolism were L-lactate and ethanol, and these compounds accounted for 86--92% of the glucose utilized. With input glucose concentrations less than 3 mV, YgluMax was found to be 40--43, YATPMax 20--21 and ms 0.1--0.2. These values are almost identical to those found previously for cultures at 25 degrees C and show that this psychrotroph grows with a very high energetic efficiency over a wide range of temperatures. With a higher (but still limiting) input glucose concentration of 5.6 mM at 9 degrees C, cellular efficiency declined as there was a marked reduction in Yglu. This decrease was accounted for in mathematical terms by an increase in ms to 0.7, whilst YgluMax and gh energetic efficiency over a wide range of temperatures. With a higher (but still limiting) input glucose concentration of 5.6 mM at 9 degrees C, cellular efficiency declined as there was a marked reduction in Yglu. This decrease was accounted for in mathematical terms by an increase in ms to 0.7, whilst YgluMax and gh energetic efficiency over a wide range of temperatures. With a higher (but still limiting) input glucose concentration of 5.6 mM at 9 degrees C, cellular efficiency declined as there was a marked reduction in Yglu. This decrease was accounted for in mathematical terms by an increase in ms to 0.7, whilst YgluMax and YATPMax remained high at 38 and 19 respectively.