Anaerobic haloalkaliphiles

Halo-alkali-philes is a type of double extremophiles functioning optimally in saline brines of soda lakes. Soda lakes are a specific type of salt lakes with their brines consisting mostly of alkaline sodium carbonates. With rare exceptions, the haloalkaliphiles are prokaryotes, represented by four major metabolic blocks: aerobic and anoxygenic
phototrophs as primary producers and aerobicand anaerobic chemotrophs mostly involved in mineral cycling and mineralisation of organic carbon. The fermentative anaerobes in soda lakes mostly include members of Clostridia involved in polymer hydrolysis and further fermentationof the monomers. The halolalkaliphilic denitrifiers are represented mostly by the members of Gammaproteobacteria from the genera Halomonas and Alkalilimnicola/Alkalispirillum group. The sulfidogens is the most active group of secondary
anaerobes in soda lakes and include two major groups – sulfate/thiosulfate reducers from the Deltaproteobacteria with a prominent capacity for sulfite and thiosulfate disproportionation and sulfur/polysulfide reducers from the phylum Chrysiogenetes. Furthermore, soda lake natronoarchaea can also participate in polysulfide respiration.
Methanogenesis in soda lakes is active with all three classical pathway represented by haloalkaliphilic species, but, similar to salt lakes, it is dominated by methylotrophs. So far, little is known about the specific bioenergetic features of the soda lake anaerobes allowing them to thrive at high pH. One of it, however, seems to be in common – the substantial use of sodium-pumping, both by primary and secondary cation pumps.