| Summary: | Electroactive bacteria have a wide range of applications, including electricity production, bioremediation, and the sensing of toxic compounds. Bacterial biofilm formation is often mediated by the second messenger cyclic guanosine monophosphate (c-di-GMP) synthesized by a diguanylate cyclase (DGC). The role of c-di-GMP in the expression of c-type cytochromes has been previously reported. The aim of this study was to determine the bioelectrogenic activity of <i>Cupriavidus metallidurans</i> strain CH34 pJB<i>pleD</i>*, which possesses a constitutively active DGC that increases c-di-GMP levels. Notably, the heterologous expression of the constitutively active DGC in <i>C. metallidurans</i> strain CH34 pJB<i>pleD</i>* showed a higher biofilm formation and increased the electrical current production up to 560%. In addition, <i>C. metallidurans</i> CH34 pJB<i>pleD</i>* showed increased levels of c-type cytochrome-associated transcripts compared with the wild-type strain CH34. Scanning electron microscopies revealed a denser extracellular matrix with an increased exopolymeric substance content in the CH34 pJB<i>pleD</i>* biofilm on the electrode surface. The results of this study suggest that higher levels of c-di-GMP synthesized by a constitutively active diguanylate cyclase in <i>C. metallidurans</i> strain CH34 pJB<i>pleD</i>* activated the formation of an electroactive biofilm on the electrode, enhancing its exoelectrogenic activity.
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