Aims: Resistance to acidic stress contributes to bacterial persistence in the host and is thought to promote their passage through the human gastric barrier. The aim of this study was to examine whether nucleosides have a role in the survival under acidic conditions in Escherichia coli. Methods and Results: We found that adenosine has a function to survive against extremely acidic stress. The deletion of add encoding adenosine deaminase that converts adenosine into inosine and NH3 attenuated the survival in the presence of adenosine. The addition of adenosine increased intracellular pH of E. coli cells in pH 2 5 medium. Addition of inosine or adenine did not increase the resistance to acidic conditions. Conclusions: Our present results imply that adenosine was used to survive under extremely acidic conditions via the production of NH3. Significance and Impact of the Study: It has been proposed that amino acid decarboxylation is the major system for the resistance of E. coli to acidic stress. In this study, the adenosine deamination was shown to induce the survival under acidic conditions, demonstrating that bacteria have alternative strategies to survive under acidic conditions besides amino acid decarboxylation.