Osmo- and thermo-adaptation in hyperthermophilic Archaea: identification of compatible solutes accumulation profiles, and biosynthetic routes in Archaeoglobus spp.

Dissertation presented to obtain the Ph.D degree in BiochemistryHyperthermophilic organisms have optimum growth temperatures above 80°C and belong to genera that are placed near the root of the Tree of Life, in short phylogenetic branches within the domains Bacteria or Archaea. Although hyperthermophiles have been isolated from a variety of hot environments, most species originate from marine geothermal areas, hence they are slightly halophilic. The accumulation of low-molecular mass organic solutes, i. e., compatible solutes, is one of the most common strategies developed by cells to cope with fluctuations of the salinity of the medium. Interestingly, in marine hyperthermophiles, compatible solute accumulation occurs not only in response to an increase in the external salt concentration, but also in response to supraoptimal growth temperatures. Moreover, microorganisms adapted to grow optimally at elevated temperatures tend to use negatively charged solutes that are not present or rarely encountered in mesophilic organisms.(...