Microbial electrochemical systems (MECs) exploit the ability of electrogenic bacteria to transfer electrons to solid electrodes, thereby generating electricity or driving chemical synthesis. Model organisms such as Geobacter sulfurreducens and Shewanella oneidensis demonstrate how extracellular electron transfer (EET) can be harnessed in microbial fuel cells and electrolysers. While these systems show great promise, the performance of these devices depends on numerous factors, including pH, ionic strength and nutrient availability. Among those, magnesium has emerged as an especially important micronutrient because of its integral role in microbial physiology and its potential to influence electron transfer rates.This study examines how magnesium availability affects T. acetexigens performance. T. acetexigens is notable for its ability to produce current densities exceeding 9 A m-2 and possesses multiple co-existing EET pathways including large multi-heme cytochromes with up to 86 heme-binding motifs. Previously, we observed that the requirements for magnesium in growth media are significantly higher for T. acetexigens, compared to other EET bacteria, such as G. sulfurreducens. DSMZ (German Collection of Microorganisms) medium 148 for T. acetexigens specifies 1.6 mM MgSO4, whereas medium 826 for G. sulfurreducens contains only 0.12 mM. This represents a more than 13-fold difference in magnesium requirements. This observation prompted us to investigate how magnesium affects EET mechanisms, survivability and biofilm development along with associated changes on proteome level in T. acetexigens.