Cable bacteria (Ca. Electrothrix) are long, filamentous, multicellular bacteria that grow in marine sediments and couple sulfur oxidation to oxygen reduction over centimeter-scale distances via an enigmatic long-distance electron transport mechanism. They can grow to tremendous densities and strongly modify the sediment environment in multiple ways, including efficient sulfide removal, stimulation of sulfate reduction, and alteration of porewater pH distribution. In this thesis, I asked if cable bacteria can influence the sympatric microbial community composition and activity, using a time-series manipulation experiment. As anticipated, based on their influence on sediment geochemistry, cable bacteria growth was associated with the stimulation of several genera of sulfate-reducing bacteria, and a sulfur-disproportionating genus (Desulfocapsa). I observed a positive relationship with the OM27 clade of the predatory Bdellovibrionota. Finally, I detected evidence of interaction with two chemoautotrophic sulfur oxidizers (Thiogranum, Sedimenticola), which are good candidates for further examination of potential electrical connection with cable bacteria.