the co-occurrence of Geobacter and Methanosarcinales is often used as a proxy for the manifestation of direct interspecies electron transfer (Diet) in the environment. Here we tested eleven new coculture combinations between methanogens and electrogens. previously, only the most electrogenic Geobacter paired by Diet with Methanosarcinales methanogens, namely G. metallireducens and G. hydrogenophilus. Here we provide additional support, and show that five additional Methanosarcinales paired with G. metallireducens, while a strict hydrogenotroph could not. We also show that G. hydrogenophilus, which is incapable to grow with a strict hydrogenotrophic methanogen, could pair with a strict non-hydrogenotrophic Methanosarcinales. Likewise, an electrogen outside the Geobacter cluster (Rhodoferrax ferrireducens) paired with Methanosarcinales but not with strict hydrogenotrophic methanogens. the ability to interact with electrogens appears to be conserved among Methanosarcinales, the only methanogens with c-type cytochromes, including multihemes (MHc). nonetheless, MHc, which are often linked to extracellular electron transfer, were neither unique nor universal to Methanosarcinales and only two of seven Methanosarcinales tested had MHc. of these two, one strain had an MHc-deletion knockout available, which we hereby show is still capable to retrieve extracellular electrons from G. metallireducens or an electrode suggesting an MHcindependent strategy for extracellular electron uptake.Direct interspecies electron transfer (DIET) was discovered in an artificial co-culture of an ethanol-oxidizing Geobacter metallireducens with a fumarate-reducing Geobacter sulfurreducens where the possibility of hydrogen gas (H 2 ) or formate transfer was invalidated through genetic studies 1,2 . Gene deletions rendering H 2 and formate transfer impossible resulted in active co-cultures 1,2 , whereas deletion of genes for extracellular electron transfer proteins (EET) such as pili, and multiheme c-type cytochromes made the interspecies interaction impossible 1,3 . Remarkably, a deletion mutant lacking an outer membrane multiheme c-type cytochrome (OmcS) could be rescued by the addition of extracellular conductive particles, whereas a pili knock-out strain could not be rescued by conductive particles 4 . Additionally, previous studies have shown that G. metallireducens is also highly effective as an anode-respiring bacteria (ARB) generating some of the highest current densities of all Geobacter tested 5 . During DIET with G. sulfurreducens, G. metallireducens requires pili and certain multiheme c-type cytochromes 3 , which were also required during anode respiration 6,7 .G. metallireducens is a strict respiratory microorganism unable to ferment its substrates to produce H 2 for interspecies H 2 -transfer 8,9 . Consequently, G. metallireducens could not provide reducing equivalents for strict hydrogenotrophic methanogens (Methanospirilum hungatei and Methanobacterium formicicum) 10,11 . However, G. metallireducens did interact syntrophically wi...