representing together no more than 0.1% of the population of each salt), all archaea belonged to the Halobacteriaceae family (Fig. 3). Its members are all halophiles thriving in hypersaline habitats including crystallizer
ponds and salt mines from where many food-grade salts have been extracted. Among the 40 genera of this family, 30 have been identified in at least one of the salts and 21 are present in at least 7 of the 9 salts
analyzed.
The diversity of archaeal genera identified per salt ranges from 21 (Hâlen Môn) to 27 (Guérande and Dead Sea). The main genera and their relative abundance strongly differ among salts. Four salts display a single major genus (Palm Island black, Black Sea, Hâlen Môn and Maras) while the other five have three or more genera with similar occurrence
(Fig. 4). Halorubrum is themost abundant genus in HâlenMôn and Black Sea salts. In the latter, the 16S rRNA gene frequency of Halorubrum reaches 84.3%. The gene frequency of Haloarcula accounts for 53.9% of the archaeal population in Maras salt and Halonotius is the majority genus in Palm Island black salt with a gene frequency of
53.1%. In Lac Rose salt, the archaeal diversity is dominated by three genera: Haloarcula (23.4%), Halorubrum (19.5%) and Natronomonas (16.9%) whereas in Dead Sea salt, 79.4% of the population is made up by 4
genera: Halorubrum (26.5%), Halomicrobium (23.2%), Halorhabdus (18.1%) and Halobacterium (11.5%).