Salt Stress Response of Sulfolobus acidocaldarius Involves Complex Trehalose Metabolism Utilizing a Novel Trehalose-6-Phosphate Synthase (TPS)/Trehalose-6-Phosphate Phosphatase (TPP) Pathway.

The crenarchaeon has been described to synthesize trehalose via the maltooligosyltrehalose synthase (TreY) and maltooligosyltrehalose trehalohydrolase (TreZ) pathway, and the trehalose glycosyltransferring synthase (TreT) pathway has been predicted. Deletion mutant analysis of strains with single and double deletions of Δ and Δ in revealed that in addition to these two pathways, a third, novel trehalose biosynthesis pathway is operative : the trehalose-6-phosphate (T6P) synthase/T6P phosphatase (TPS/TPP) pathway. In contrast to known TPS proteins, which belong to the GT20 family, the TPS belongs to the GT4 family, establishing a new function within this group of enzymes. This novel GT4-like TPS was found to be present mainly in the The Δ Δ Δ triple mutant of , which lacks the ability to synthesize trehalose, showed no altered phenotype under standard conditions or heat stress but was unable to grow under salt stress. Accordingly, in the wild-type strain, a significant increase of intracellular trehalose formation was observed under salt stress. Quantitative real-time PCR showed a salt stress-mediated induction of all three trehalose-synthesizing pathways. This demonstrates that in , trehalose plays an essential role for growth under high-salt conditions. The metabolism and function of trehalose as a compatible solute in was not well understood. This combined genetic and enzymatic approach at the interface of microbiology, physiology, and microbial ecology gives important insights into survival under stress, adaptation to extreme environments, and the role of compatible solutes in Here, we unraveled the complexity of trehalose metabolism, and we present a comprehensive study on trehalose function in stress response in This sheds light on the general microbiology and the fascinating metabolic repertoire of , involving many novel biocatalysts, such as glycosyltransferases, with great potential in biotechnology.