Calorimetric real time monitoring of lambda prophage induction

Calorimetry can be used for a noninvasive monitoring of metabolic and energy changes in bacterial cultures in real time. This potentially includes changes occurring during phage infection cycles. To demonstrate this, the growth of Escherichia coli K124 F(-) carrying the lambda prophage was monitored in a reaction calorimeter, while inducing the shift from lysogeny to lysis using methotrexate (MTX) as the inducer. Different phases of the phage infection were distinguishable calorimetrically. The calorimetric signals corresponded well to changes in growth stoichiometry and kinetics that were measured non-calorimetrically. The comparison of the calorimetric results with other measurements of activity revealed that the calorimetric method was superior since the calorimetric data mirrored the progress of infection in more detail. Contradictions between the calorimetric data and the appearance of infectious phages could result from inactivation of phage by MTX.