Microbial fuel cells that can generate energy out of wastewaters are close to pilot scale testing. As such, MFC technology is complementary to methane generation due to the possibility to rapidly convert organic acids, polish effluents and work at low substrate concentrations. The main bottleneck perceived at the moment is the cathodic electron transfer. A variety of catalysts has been investigated for the direct transfer of electrons from the cathode to oxygen in the air. Overlooked in this context were bacteria. Bacteria could indeed be worthwhile to replace chemical catalysts. Moreover, their versatility enables us to not only target at oxygen, but also at nitrous oxides and contaminants as possible drivers of electricity generation, nutrient removal and bioremediation. This paper addresses several recent developments in MFC cathode research, and demonstrates that energy generation is but an aspect of this versatile technology.