The conductive biofilms of Geobacter sulfurreducens have potential applications in renewable energy, bioremediation, and bioelectronics. In an attempt to alter biofilm properties, genes encoding proteins with a PilZ domain were deleted from the G. sulfurreducens genome. A strain, in which the gene GSU1240 was deleted, designated strain CL-1, formed biofilms much more effectively than did the wild-type strain. Increased production of pili and exopolysaccharide were associated with the enhanced biofilm production. When grown with an electrode as the electron acceptor CL-1 produced biofilms that were 6-fold more conductive than wild-type biofilms. The greater conductivity lowered the potential losses in microbial fuel cells, decreasing the charge transfer resistance at the biofilm–anode surface by ca. 60% and lowering the formal potential by 50 mV. These lower potential losses increased the potential energy of electrons reaching the biofilm–anode interface and enabled strain CL-1 to produce 70% higher power densities than the wild-type strain. Current-producing biofilms were highly cohesive and could be peeled off graphite electrodes intact, yielding a novel conductive biological material. This study demonstrates that simple genetic manipulation can yield improved bioelectronics materials with energy applications.