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.