SURVIVAL OF, AND INDUCED STRESS RESISTANCE IN, CARBON-STARVED PSEUDOMONAS-FLUORESCENS CELLS RESIDING IN SOIL

We investigated the survival, cell length, and development of general stress resistance in populations of Pseudomonas fluorescens R2f and it s rifampin-resistant mutant, R2f Rp(r), following exposure to carbon s tarvation conditions in liquid cultures and residence in two different soils, Flevo silt loam (FSL) and Ede loamy sand (ELS). In much the sa me way as was recently shown for P. putida KT2442, carbon-starved P. f luorescens R2f populations revealed enhanced resistance to otherwise l ethal treatments, such as exposure to ethanol, high temperature, osmot ic tension, and oxiidative stress, 4 large population of nonculturable P. fluorescens R2f Rp(r) cells arose shortly after their introduction into ELS soil, whereas the formation of nonculturable cells was not o bserved in FSL soil. Also, the inoculant cell (based on immunofluoresc ence) and CFU counts decreased faster in ELS soil than in FSL soil, In troduction of carbon-starved instead of exponential-growth-phase R2fRp (r) cells into ELS soil did not affect bacterial survival, The inocula nt cell length decreased in soil, and no large differences in cell len gth in the two soil types were observed. Addition of glucose to ELS so il resulted in a stable cell length of R2f Rp(r) cells, whereas carbon -starved cells introduced into ELS soil remained small. Exponentially growing R2f Rp(r) cells developed enhanced resistance to ethanol, high temperature, osmotic tension, and oxidative stress within 1 day in bo th soils, whereas cells introduced into ELS soil amended with glucose showed decreased resistance. Cells that were carbon starved prior to i ntroduction into ELS soil showed unchanged stress resistance levels up on residence in soil.