EFFECT OF CELL-DENSITY AND ATTACHMENT ON RESUSCITATION IN SOIL OF STARVED PSEUDOMONAS-FLUORESCENS MON787

The effect of cell density and attachment on starvation survival and r ecovery was determined using luminometry to measure activity of a lux- marked strain of Pseudomonas fluorescens MON787. Bioluminescence was f ound to be a sensitive indicator of in situ activity of P. fluorescens MON787 in soil. The activity of a bacterial inoculum could be monitor ed during growth in soil, and was found to correlate with an increase in cell numbers. Luminescence could detect decreasing activity of P. f luorescens during starvation in soil, and recovery of activity and cel l numbers following exposure to starvation and matric potential stress . The effect of localised cell density and attachment in soil on recov ery from lag phase after nutrient addition was investigated and compar ed to recovery of starved liquid cultures. Nutrient addition to starve d P. fluorescens in soil or liquid medium resulted in an immediate rec overy of activity, followed by a second increase in luminescence after 5 h. Cells exposed to both starvation and matric potential stress in soil did not show a detectable immediate increase of activity, but req uired a 5-h lag phase before recovery of both activity and cell growth . The lag phase values were not significantly different over a range o f localised cell densities. This suggests that cell density of P. fluo rescens in the range tested is not a factor which affects recovery of soil bacteria from starvation. (C) 1998 Federation of European Microbi ological Societies. Published by Elsevier Science B.V.