VIABILITY AND RESPIRATORY ACTIVITY OF PSEUDOMONAS-SYRINGAE CELLS STARVED IN BUFFER

Pseudomonas syringae cells starved in buffer released orcinol-reactive molecules and materials that absorbed ultraviolet light. The number o f cells culturable in nutrient medium decreased more rapidly than the number of intact particles determined by microscopy. The results sugge sted that starvation resulted in the lysis of an increasing number of cells, and that a fraction of the intact particles were not culturable . Starvation also resulted in a decrease in the rate of oxygen consump tion with acetate, glycerol, and succinate, but at different levels. W hereas the respiration of acetate and glycerol decreased concomitantly with culturability, the respiration of succinate decreased to levels similar to the concentration of intact cells, suggesting that all inta ct particles respired the succinate, but only the culturable cells res pired the acetate and glycerol. The results suggest that measuring the activity of the electron-transport system can overestimate the viabil ity of starved bacterial cells, and that complex metabolic activities such as the respiration of acetate and glycerol are probably better su ited for the evaluation of this parameter.