**3.1 Halocins**

Halocins, bacteriocins-like peptides and proteins produced by extremely halophilic archaea, were first discovered in 1982 by F. Rodriguez Valera [24, 25]. They are classified according to their size into two major classes: high molecular mass (protein, > 10 kDa) and low molecular mass (peptide, ≤10 kDa) called microhalocins [26, 27]. It has been shown that halocins are effective against *Haloarchaea* and *Crenarchaea* such as *Sulfolobus* spp. and *Methanosarcina thermopila*, and thus act across the main subdivision of the archaeal domain. These compounds represent a general class of antiarchaeal toxins and there is no confirmation about the inhibition of bacteria [26, 27]. Production of halocin is a practically universal feature of archaeal halophilic rods [27]. Although several halocins were identified, only some of them have been characterized and purified.
