Effects of growth temperature and lipophilic carbon sources on the fatty acid composition and membrane lipid fluidity of Acinetobacter calcoaceticus 69V

Abstract

This study explored the capability of Acinetobacter calcoaceticus 69V for homeoviscous adaptation. The saturation degree of the organisms's fatty acids increased as the growth temperature was raised. This response was correlated with an increase in the flourescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) intercalated in the bilayers of liposomes prepared from the cells, indicating that the fluidity of their outer and cytoplasmic membranes fell as growth temperature increased. The liposomes' fluidity increased as the temperature at which it was measured was raised. The homeoviscous efficacy of the responses to increases in growth temperature was 0.3 to 0.5, according to differences between the temperature profiles of cells grown at 20 and 40 °C. However, the derived figure fell to zero at 42 °C, the maximum growth temperature of this bacterium. Similar differences in the temperature profiles of flourescence anistropy were obtained from liposomes with differing degrees of saturation in their fatty acids induced by growing the organism on various concentrations of the lipophilic substrates ethanol and phenol. Adjusting the saturation degree of the fatty acids seems to play a major role in the homeostasis of viscosity of the cytoplasmic membrane of Acinetobacter calcoaceticus 69V, a feature that is critical for stabilising its apparatus for electron transport phosphorylation (ETP) against lipophilic attack by xenobiotics.