Maintenance coefficients and rates of turnover of cell material inEscherichia coliML308 at different growth temperatures

Maintenance coefficients and rates of turnover of cell protein, cell walls and total cell phosphate were determined during the growth of Escherichia coli ML308 in fed-batch culture at different temperatures. The apparent Arrhenius activation energies (Ea) calculated for maintenance coefficients at temperatures over 30°C were 212–515 kJ· mol−1, indicative of a process thermodynamically similar to denaturation. The corresponding Arrhenius values for turnover were of a different magnitude, 44–115 kJ mol−1, more typical of enzyme-catalysed reactions. Addition of 0.5 M NaCl had a minor effect on maintenance at both temperatures. Turnover of cell material and salt homeostasis were therefore concluded to be minor components of the maintenance requirement of E. coli.