Selective enrichment on a wide polysaccharide spectrum allowed isolation of novel metabolic and taxonomic groups of haloarchaea from hypersaline lakes

Abstract

Extremely halophilic archaea (haloarchaea) of the class Halobacteria is
a dominant group of aerobic heterotrophic prokaryotic communities in
salt-saturated habitats, such as salt lakes and solar salterns. Most of the
pure cultures of haloarchaea were enriched, isolated, and cultivated on
rich soluble substrates such as amino acids, peptides or simple sugars.
So far, the evidences on the capability of haloarchaea to use different
polysaccharides as growth substrates remained scarce. However, it is
becoming increasingly obvious that these archaea can also actively participate
in mineralization of complex biopolymers, in particular cellulose and chitin–
two dominant biomass polysaccharides on the planet. Here we used an
array of commercially available homo- and heteropolysaccharides to enrich
hydrolytic haloarchaea from hypersaline salt lakes with neutral pH and from
alkaline soda lakes. This resulted in isolation of a range of halo- and natronoarchaea, respectively, belonging to already described taxa as well as several new genus-level lineages. In some cases, the isolates enriched with different polysaccharides happened to be closely related, thus representing generalistic ecotype, while the others were narrow specialists. In general, soda lakes yielded a broader range of polysaccharide-utilizing specialists in comparison to neutral salt lakes. The results demonstrated a significant diversity of halo(natrono)archaea with a previously unrecognized potential for utilization
of a broad range of natural polysaccharides in hypersaline habitats.