Assessing sources of variability in global methane emissions is a high priority topic with the increasing need to optimize predictive models of global greenhouse gas balances. In these models, the biology of the microbes involved in methane cycling is for the most part ignored, leading to unexplained variability. Methane-oxidizing bacteria (MOB) possess the ability to utilize methane, a potent greenhouse gas, for energy generation and growth, thereby providing a key ecosystem service that is highly relevant to the regulation of the global climate. MOB sub-groups (type I and II) have different responses to key controlling factors (e.g. methane and nitrogen availability). To date, observational characteristics inherent to type I and II MOB, coupled to community level molecular analyses under different conditions, suggest that MOB sub-groups adopt different life strategies. However, most findings have been based on the correlation of MOB communities to external cues, without demonstrating the underlying mechanistic causation. Thus, the dynamics of different MOB groups are central to predicting variability in methane emissions, yet their quantitative responses to environmental conditions are still poorly understood. Here, we hypothesize that methane concentration and nitrogen availability are potential key regulating factors that drive the life strategies in type I and II MOB. We propose, for the first time, to unravel the underlying mechanisms that determine the life strategies and traits of MOB using a proteomic approach in combination with molecular analyses, and biochemical and ecological studies. The overall aim is to incorporate the research results into the ecological context in-situ.