Abstract
High levels of constitutive aldehyde‐dependent light emission were obtained from non‐growing cells of Lactococcus lactis subsp. diacetylactis F712 transformed with luxA/B when they were suspended in buffered solutions. Inductions of light emission was time‐dependent and was not due to growth, synthesis of luciferase or stimulation of metabolism by fermentable carbohydrate. The major factor controlling light emission in such cells appears to be the intracellular pH value. Experiments with ionophores indicated that a transmembrane pH gradient was not essential for light emission.