Production of prodigiosin pigment by Serratia marcescens is negatively associated with cellular ATP levels during high-rate, low-cell-density growth.

Serratia marcescens is a facultatively anaerobic bacterium and the most recognized producer of the hydrophobic pigment prodigiosin. Previous work has shown that prodigiosin both increases ATP production during population lag phase and approximately doubles the stationary-phase cell yield. Here, we employed both batch and chemostat culture methods to investigate prodigiosin's role during high rate growth at low cell density as peak cellular ATP levels decline. Batch culture experiments utilizing artificial pigment induction showed an ATP reduction during low cell density growth. In addition, pigment induction during fixed growth rate chemostat culture revealed a negative correlation between cellular levels of prodigiosin and ATP (r = -0.95). Variable growth rate chemostat experiments showed an inverse relationship between ATP per cell and prodigiosin per cell during low-density growth but a direct relationship during high-density growth. Rate modeling of chemostat data quantified the pigment's effect on cellular levels of ATP for both population growth phases. Finally, prodigiosin production in a heterologous bacterium led to ATP decline. These data with intact cells complement the established in vitro proton import function of prodigiosin pigment and may indicate an energy-spilling function during high rate, low cell density growth.