This is the first whole-cell proteomic study performed on a subzero-growing permafrost-associated isolate at such a low temperature (-10C) and one that connects subzero growth and the salt response. Through whole-cell proteomic analyses at -10C, 23C, and high/low salt conditions, we could identify functional pathways and mechanisms important for subzero growth in the extremophile Planococcus halocryophilus.