Effect of high levels of CO2 and O2 on membrane fatty acid profile and membrane physiology of meat spoilage bacteria

The membrane is the major protective barrier separating the cell from the environment and is thus important for bacteria to survive environmental stress. This study investigates changes in membrane lipid compositions and membrane physiology of meat spoiling bacteria in response to high CO 2 (30%) and O 2 (70%) concentrations, as commonly used for modified atmosphere packaging of meat. Therefore, the fatty acid profile as well as membrane fluidity, permeability and cell surface were determined and correlated to the genomic settings of five meat spoiling bacteria Brochothrix (B.) thermosphacta , Carnobacterium (C.) divergens , C. maltaromaticum , Leuconostoc (L.) gelidum subsp. gelidum and L. gelidum subsp. gasicomitatum cultivated under different gas atmospheres. We identified different genomic potentials for fatty acid adaptations, which were in accordance with actual measured changes in the fatty acid composition for each species in response to CO 2 and/or O 2 , e.g., an increase in saturated, iso and cyclopropane fatty acids. Even though fatty acid changes were species-specific, the general physiological responses were similar, comprising a decreased membrane permeability and fluidity. Thus, we concluded that meat spoiling bacteria facilitate a change in membrane fatty acids upon exposure to O 2 and CO 2 , what leads to alteration of membrane fluidity and permeability. The observed adaptations might contribute to the resistance of meat spoilers against detrimental effects of the gases O 2 and CO 2 and thus help to explain their ability to grow under different modified atmospheres. Furthermore, this study provides fundamental knowledge regarding the impact of fatty acid changes on important membrane properties of bacteria.