TECHNOLOGY FOCUS - BIOLOGY - Preferred Organism: The microorganisms produce electrons which are collected by the anode, and comprise sulfur-oxidizing bacteria, archaea, or eukarya. The microorganisms are Arcobacter, Chromatium, Chlorobium, Beggiatoa, Thiothrix, Thiobacillus, Acidithiobacillus, Thiomicrospira, and/or Desulfuromonas. At least some of microorganisms are aerobic or anaerobic.    TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Component: The fuel cell is poised by an active or passive potentiostat, where potential is directly controlled by electronic control, or where the potential created by microbial activity is altered through varying the resistance. The fuel cell further has a load connected to anode and cathode. The load comprises light, motor, energy storage device, switching circuit, or other device requiring an electric current.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compound: The sulfur-containing compound is H2S, HS-, S2-, thiosulfate, elemental sulfur, polysulfide, and/or mercaptan of formula: RSR'. The source further comprises fuel and microorganisms which are configured selectively oxidize the sulfur-containing compound without substantial oxidation of the fuel. The fuel is methane, ethane, propane, butane, pentane, pentane, hexane, heptane or octane. The anode and cathode are separated by a proton exchange interface. The proton exchange interface is polymeric interface. The proton exchange interface is permeable to hydrogen ions. The proton exchange interface is non-polymeric. The proton exchange interface is packed bead column. The cathode is capable of converting carbon dioxide to carbonate or bicarbonate salt of sodium, calcium, barium, magnesium, or potassium. The source of carbon dioxide is microorganisms, and/or exogenous source of carbon dioxide. The exogenous source of carbon dioxide is compressed carbon dioxide gas. The carbonic acid is produced by microorganisms. The carbonic acid is formed by dissolving exogenous source of carbon dioxide in water.R=optionally substituted phenyl;andR'=H.R and R' are not H simultaneously.