They believe the bugs could be used as microbial batteries turning plant and animal waste into energy.
The bacteria could be employed in domestic sewage plants, or to generate power as they clean up lakes and coastal seas laid waste by organic pollutants.
To demonstrate the idea, scientists built a laboratory microbial battery consisting of electrodes dipped into a bottle of waste water.
In the bottle, an unusual strain of bacteria feast on organic waste particles and produce electricity captured by the positive electrode.
"We call it fishing for electrons," said environmental engineer Professor Craig Criddle, from Stanford University in the US.
The researchers estimate that the bugs can extract about 30% of the potential energy locked in organic waste water - an efficiency roughly equal to the best solar cells that convert sunlight into electricity.
Scientists know so-called "exoelectrogenic microbes" that evolved in airless environments have potential as bio-generators. But tapping the energy they produce has proved difficult.
The new microbial battery is described in the latest edition of the journal Proceedings of the National Academy of Sciences.