Carbon dioxide increases acid resistance in Escherichia coli

Aims: To investigate how carbon dioxide affects the acid resistance of Escherichia coli. Methods and Results: Escherichia coli W3110 was grown in minimal EG medium at pH 7 5, and cells were adapted at pH 5 5 at 37 degrees C with and without supply of carbon dioxide and nitrogen gases. The number of colonies grown on LB medium was measured after cells were challenged in minimal EG medium of pH 2 5 at 37 degrees C under various conditions. When carbon dioxide was supplied at both the acid adaptation and challenge stages, 94% of cells survived after the acid challenge for 1 h, while the survival rates were 50 and 67% when nitrogen gas and glutamate were supplied respectively. After the acid challenge for 3 h, the survival rate observed with the carbon dioxide gas supply was again 2.5-fold higher than those with the nitrogen gas supply. Conclusion: Carbon dioxide was shown to participate in the maintenance of high viability under acidic conditions. Significance and Impact of the Study: This study provides useful information for research into bacterial pathogenesis, fermentation and food preservation.