Positive, Neutral and Negative Interactions in Cocultures between Pyrococcus furiosus and Different Methanogenic Archaea

The model organism Pyrococcus furiosus has recently been reported to interact with Methanopyrus kandleri in coculture, suggesting a H2 symbiosis. In the current study we further investigated this hypothesis by growing P. furiosus with four other hyperthermophilic methanogens providing evidence that the organisms did not only exert positive effects (P. furiosus/Methanocaldococcus villosus and P. furiosus/Methanocaldococcus infernus) on each other, but also neutral (P. furiosus/Methanocaldococcus jannaschii) and even inhibitory interactions (P. furiosus/Methanotorris igneus) were detected suggesting interspecies relationships not only based on H2 symbiosis. Using various microscopic techniques we further analyzed the coculture with the highest positive interactions (P. furiosus/ M. villosus) concerning its growth behavior on various surfaces, which turned out to be in stark contrast to the previous reported coculture of P. furiosus/M. kandleri. This communication provides new insights into possible interactions of extremophilic Archaea in co-cultures and again raises the question if and how hyperthermophilic Archaea communicate besides metabolic intermediates like H2.