The effect of sodium chloride or PEG8000 on the degree of saturation of membrane fatty acids. The ratios of saturated to unsaturated fatty acids were measured in control cultures (grey bars), after perturbation with sodium chloride (black bars), or after perturbation with PEG8000 (white bars). Measurements were made after short-term perturbation (30 min) or long-term perturbation (24 hour). All measurements are averages from three biological cultures and error bars are one standard deviation. Asterisks (*) indicate measurements that are statistically different from the controls (p-value < 0.05).