Example from liiterature: Functional pathways at KEGG database (level) 3 affiliated to energy metabolism. Oxidative phosphorylation (ko00190)  and methane metabolism (ko00680, mainly referred to methanogenesis in anaerobic environments) were dominant at all temperatures with the latter more pronounced at thermophilic temperatures (50° C). Beyond this temperature, the lower portions of Euryarchaeota in the relative abundances of this pathway suggests that 50 °C might be the threshold temperature within which an increased temperature improves methane production in this specific AD system. Reproduced with permission from \cite{Lin_2016a}. Copyright Elsevier.