CO 2 - and Anaerobiosis-Induced Changes in Physiology and Gene Expression of Different Listeria monocytogenes Strains

Abstract

ABSTRACT Although carbon dioxide (CO 2 ) is known to inhibit growth of most bacteria, very little is known about the cellular response. The food-borne pathogen Listeria monocytogenes is characterized by its ability to grow in high CO 2 concentrations at refrigeration temperatures. We examined the listerial responses of different strains to growth in air, 100% N 2 , and 100% CO 2 . The CO 2 -induced changes in membrane lipid fatty acid composition and expression of selected genes were strain dependent. The acid-tolerant L. monocytogenes LO28 responded in the same manner to CO 2 as to other anaerobic, slightly acidic environments (100% N 2 , pH 5.7). An increase in the expression of the genes encoding glutamate decarboxylase (essential for survival in strong acid) as well as an increased amount of branched-chain fatty acids in the membrane was observed in both atmospheres. In contrast, the acid-sensitive L. monocytogenes strain EGD responded differently to CO 2 and N 2 at the same pH. In a separate experiment with L. monocytogenes 412, an increased isocitrate dehydrogenase activity level was observed for cells grown in CO 2 -containing atmospheres. Together, our findings demonstrate that the CO 2 -response is a partly strain-dependent complex mechanism. The possible links between the CO 2 -dependent changes in isocitrate dehydrogenase activity, glutamate metabolism and branched fatty acid biosynthesis are discussed.