Three genera isolated in Guérande salt were not found in the corresponding metagenomic analysis: Halobellus, Halolamina and Halopenitus. As the 16S rRNA gene sequences of their type strains is covered by the primers used in the analysis, it seems most likely that their absence is caused by either a low occurrence in the archaeal community or a poor efficiency in the extraction of their DNA, possibly caused by some peculiarities in their cellular structure.