Persistence of regulation of macromolecular synthesis by Escherichia coli during killing by disrupted rabbit granulocytes

Abstract

Escherichia coli incubated in balanced salt solution with glucose as a carbon source but no nitrogen source exhibit a marked step-up of macromolecular synthesis when various non-bactericidal tissue extracts, or fractions thereof, are added. When disrupted granulocytes that cause rapid loss of viability are added, a step-up is also observed; i.e., incorporation of labeled precursors into ribonucleic acid is stimulated more than 15-fold, and incorporation into protein and deoxyribonucleic acid about twofold. This stimulation of macromolecular synthesis is still evident 30 min after more than 95% of the E. coli have lost their ability to multiply. Stimulation by disrupted granulocytes of [(14)C]leucine incorporation into E. coli protein occurs over a wide range of leucine concentrations but is usually eliminated by adding a Casamino Acids mixture or another more complete medium. The substance(s) in tissue homogenates that trigger step-up is heat stable and dialyzable. Thus, E. coli exposed to the bactericidal and digestive components of disrupted granulocytes and no longer capable of division maintain their ability to regulate macromolecular synthesis in response to changes in nutritional conditions for at least 1 h.