ABSTRACT: Halohasta litchfieldiae and Halorubrum lacusprofundi are important members of Deep Lake in Antarctica, representing ~44% (the most abundance) and ~10% (the 3rd most abundance) of the lake population. Deep Lake is in the Vestfold Hills, East Antarctica (68°33’36.8S, 78°11’48.7E) and is 36 m deep, monomictic, and perennially cold (down to -20C) (DeMaere et al., 2013; Williams et al., 2014; Tschitschko et al., 2015; Tschitschko et al., 2016). In this project, using quantitative proteomics (8-plex iTRAQ labeling), proteins, pathways and cellular processes important for cold adaptation were determined for both Hht. litchfieldiae and Hrr. lacusprofundi. The data provided a new level of understanding about molecular mechanisms and regulatory networks involved in adaptation of the Antarctic haloarchaea to cold environment. DeMaere, M. Z., Williams, T. J., Allen, M. A., Brown, M. V., Gibson, J. A., Rich, J., et al. (2013) High level of intergenera gene exchange shapes the evolution of haloarchaea in an isolated Antarctic lake. Proc Natl Acad Sci USA 110: 16939-16944. Tschitschko, B., Williams, T. J., Allen, M. A., Páez-Espino, D., Kyrpides, N., Zhong, L., et al. (2015) Antarctic archaea–virus interactions: metaproteome-led analysis of invasion, evasion and adaptation. ISME J 9: 2094-2107. Tschitschko, B., Williams, T. J., Allen, M. A., Zhong, L., Raftery, M. J., and Cavicchioli, R. (2016) Ecophysiological distinctions of haloarchaea from a hypersaline Antarctic lake determined using metaproteomics. Appl Environ Microbiol 82: 3165 – 3173. Williams, T. J., Allen, M. A., DeMaere, M. Z., Kyrpides, N. C., Tringe, S. G., Woyke, T., and Cavicchioli, R. (2014) Microbial ecology of an Antarctic hypersaline lake: genomic assessment of ecophysiology among dominant haloarchaea. ISME J 8: 1645-1658.