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The Escherichia coli bacteria have three inducible H+-consuming Acid Resistance (AR) systems (Gad, Adi, Cad). The entire mechanisms and importance of AR systems in the formation of bioenergetic parameters, and interaction with other H+ consuming complexes (such as formate hydrogen lyase) and ion transport mechanisms are not well-known. In the current project, the involvement of AR systems in the formation of bioenergetic parameters in E. coli during fermentation or respiration at different pHs (pH 4.4-7.5) will be understood. Proton motive force and its variation in the E. coli mutants lacking AR systems (∆gadE, ∆cadC and ∆adiY) will be detected. The role of AR systems in the formation of ion fluxes and ionic homeostasis will be understood. Moreover, the interaction between the production of metabolic end-products (acids and molecular hydrogen) and AR systems during fermentation of different carbon sources (glucose, glycerol) will be described. Based on the acquired data, a mechanism will be presented and a prototype will be suggested elucidating how bacteria regulate bioenergetic parameters and implement AR systems to withstand mild and extreme acidic conditions.