Archaeal genomes encode histone proteins that resemble those of eukaryotic H3 and H4 and wrap DNA in vitro. However, the in vivo function of these proteins remains unclear. Further, histone function has never been investigated in hypersaline-adapted archaea. These organisms encode an unusual fused histone dimer that may represent an evolutionary intermediate. Our recent data suggest that halophilic histone protein is required to maintain proper cell shape and size during cellular division. Histone is also required for appropriate gene activation across the genome during growth. This project seeks to further understand the function of histones in chromatin compaction, gene regulation, and cell physiology in halophiles.