Extreme halophilic environments - including salt lakes and springs, seawater evaporation facilities for the production of sea salt, and subterranean salt deposits derived from ancient oceans - are distributed patchily all over the world. The life that dominates them is microbial (e.g., prokaryotes and the viruses that infect them). The best studied in these environments are the haloarchaea (family Halobacteriaceae), a diverse group of salt-loving organisms in the archaeal phylum Euryarchaeota. These remarkable organisms have an obligate requirement for salt concentrations between 10% and 35%...