Extracellular factors responsible for the adaptation ofPseudomonas fluorescens batch cultures to unfavorable conditions

The culture liquid filtrate of an exponential-phasePseudomonas fluorescens batch culture added to anotherP. fluorescens culture at the moment of inoculation was found (1) to prevent or diminish cell adsorption of the flask walls, (2) to enhance the intensity of cell respiration, (3) to shorten the period of adaptation of LB-grown cells to growth in glucose-containing mineral M9 medium, (4) to stimulate bacterial growth at supraoptimum temperature (36°C) and pH values (4.8 and 9.2), and (5) to decrease the death rate of bacteria at the supraoptimum growth temperature. These results were interpreted as indicating thatP. fluorescens cultures produce two types of regulatory exometabolites similar to those revealed earlier inEscherichia coli andBacillus subtilis cultures: the direct-action adaptogenic factorX ₁ capable of increasing bacterial resistance to unfavorable growth conditions (temperature and pH) and factor of accelerated adaptation to new media. Both factors are presumably low-molecular-weight hydrophilic nonprotein compounds.