Desulfotomaculum orientis is able to switch its life style from being a sulfate-reducing respiring organism to becoming a fermenter if the environment gets depleted of sulfate. It converts methanol via the acetyl-CoA pathway to acetate in the absence of sulfate and it produces hydrogensulfide as long as sulfate is present. In the exercise we will apply thermodynamic approaches to evaluate dissimilation and assimilation reactions under sulfate-reducing and acetogenic conditions and analyze the thermodynamic differences between the beginning and the end of the incubation in a batch culture.