When a bacterial species survives under changing environmental circumstances (e.g. salinity or temperature), its proteins might not function in all physicochemical conditions. We propose that prokaryotes cope with this problem by having two or more copies of the genes affected by environmental fluctuations, each one performing the same function under different conditions (i.e. ecoparalog). We identify potential examples in the bacterium Salinibacter ruber and in other species that experience wide environmental variations.