The degradation of glycosaminoglycans by haloarchaea is apparently a common feature in hypersaline habitats worldwide

Recent extensive studies of the functional diversity of extremely halophilic archaea (haloarchaea) have significantly altered the long-held view of this unique group of extremophiles as halophilic heterotrophs utilizing either rich mixtures of amino acids or simple soluble monomeric compounds such as sugars or organic acids. Our recent efforts clearly demostrated that many haloarchaeal species possess significant hydrolytic potential for decomposition of various groups of difficult-to-degrade polysaccharides. However, so far, there was no evidence that these archaea can utilize acidic polysaccharides. In this study, we characterized three strains of haloarchaea isolated from brine and sediment samples from various regions of Eurasia, namely, hypersaline lakes of the Kulunda Steppe in Russia, marine solar salterns of Samouco in Portugal and Trapani in Italy, and salt production fields of Nha Trang and Cam Ranh in Vietnam, using hyaluronic acid (HA) as the sole carbon and energy source as an enrichment substrate. The isolates utilizing this glycosaminoglycan (GAG) were identified as new-species members of the genera Natronoarchaeum and Haloarcula . Apart from the HA they can also grow with another GAG - chondroitin sulfate A. Genome analysis of these strains identified the genes potentially encoding the enzymes responsible for their GAG-degrading activity and determined the origin of these genes. This type of metabolism was unknown in haloarchaea prior to this study, potentially allowing haloarchaea to thrive on a rather specific polysaccharides, uncharacteristic of hypersaline ecosystems. These results further confirm that haloarchaea represent a unique group of extreme halophiles with incredibly extensive metabolic capabilities, representing a vast, largely unknown reservoir of functional diversity and having strong ecological significance in carbon cycling in hypersaline ecosystems worldwide and promising biotechnological potential.