Adaptation of Pseudomonas putida S12 to ethanol and toluene at the level of fatty acid composition of membranes.

Pseudomonas putida S12 was more tolerant to ethanol when preadapted to supersaturating concentrations of toluene. Cellular reactions at the membrane level to the toxicities of both compounds were different. In growing cells of P. putida S12, sublethal concentrations of toluene resulted in an increase in the degree of saturation of the membrane fatty acids, whereas toxically equivalent concentrations of ethanol led to a decrease in this value. Contrary to this, cells also reacted to both substances with a strong increase of the trans unsaturated fatty acids and a corresponding decrease of the cis unsaturated fatty acids under conditions where growth and other cellular membrane reactions were totally inhibited. While the isomerization of cis to trans unsaturated fatty acids compensates for the fluidizing effect caused by ethanol, a decrease in the degree of saturation is antagonistic with respect to the chemo-physical properties of the membrane. Consequently, the results support the hypothesis that the decrease in the degree of saturation induced by ethanol is not an adaptation mechanism but is caused by an inhibitory effect of the compound on the biosynthesis of saturated fatty acids

Physiological response of Pseudomonas putida S12 subjected to reduced water activity.

The effect of osmotic stress, given as decreased water activity (aw), on growth and the accumulation of potassium and the compatible solute betaine by Pseudomonas putida S12 was investigated. Reduced aw was imposed by addition of sodium chloride, sucrose, glycerol or polyethylene glycol to the growth medium. Accumulation of potassium and betaine was established when sodium chloride and sucrose were used to cause osmotic stress. No accumulation of these solutes was found in the presence of glycerol. Addition of polyethylene glycol to the medium strongly decreased the growth rate in comparison with the other osmolytes tested at the corresponding aw. Although polyethylene glycol did decrease the aw, neither potassium nor betaine was accumulated by the cells

Physiological response of Pseudomonas putida S12 subjected to reduced water activity.

The effect of osmotic stress, given as decreased water activity (aw), on growth and the accumulation of potassium and the compatible solute betaine by Pseudomonas putida S12 was investigated. Reduced aw was imposed by addition of sodium chloride, sucrose, glycerol or polyethylene glycol to the growth medium. Accumulation of potassium and betaine was established when sodium chloride and sucrose were used to cause osmotic stress. No accumulation of these solutes was found in the presence of glycerol. Addition of polyethylene glycol to the medium strongly decreased the growth rate in comparison with the other osmolytes tested at the corresponding aw. Although polyethylene glycol did decrease the aw, neither potassium nor betaine was accumulated by the cells