The soil environment contains the largest pool of carbon on Earth, with controls on soil carbon residency and flux being an emergent property of microbial metabolism. Despite the fact that microbial interactions have metabolic implications, the contribution of interactions are often overlooked regarding the carbon cycle. Here, we hypothesize that microbial interactions are intrinsically coupled to carbon cycling through eco-evolutionary principles. Interactions drive phenotypic responses that result in allocation pattern shifts and changes in carbon use efficiency. These changes promote alterations in resource availability and community structure, thereby creating selective pressures that contribute to diffuse evolutionary mechanisms. The outcomes then feed back into microbial metabolic operations with consequences for carbon turnover, continuing a feedback loop of microbial interactions, evolutionary processes, and the carbon cycle.