Updated project metadata. Proteorhodopsin has been an ongoing hot topic for the past decade. However the complete physiological role of this extremely widely distributed protein remains mysterious. In this study we aim to give an insight to the physiology of a proteorhodopsin-containing sea ice bacteria – Psychroflexus torquis using gel-free label-free proteomic approach for the first time. We also addressed the life strategy that used by this organism to successfully inhabit extreme sea ice environment.