Temperature Dependence of Growth and Fatty Acid Composition in the Cell Membrane of Mesophilic Bacteria Grown below the Optimum Growth Temperature

The features of Arrhenius plots of the relationship between specific growth rate and temperature for four strains of mesophilic bacteria varied depending on the cultivation temperature of the seed. An inflection point was observed around 20°C for the seed grown at 28 to 30°C but not for the seed grown previously at 15 to 17°C. The inflection temperature coincided with the phase transition temperature (around 23°C) determined by the DSC spectra of phospholipids extracted from the cells of Lactobacillus plantarum and Escherichia coil grown at 30°C. From the comparison of fatty acid compositions of phospholipids from the cells grown at different temperatures, unsaturated fatty acids were thought to be converted to corresponding cyclopropanoic acids by transmethylation at the higher temperature. Thus it was suggested that the increase in the cyclopropanoic acids causes the decrease in the membrane fluidity and the inflection point appears in the Arrhenius plot around 20°C for the seed grown at 28 to 30°C.