The Impact of Pyroglutamate:Sulfolobus acidocaldariusHas a Growth Advantage overSaccharolobus solfataricusin Glutamate-Containing Media

Abstract

Microorganisms are well adapted to their habitat but are partially sensitive to toxic metabolites or abiotic compounds secreted by other organisms or chemically formed under the respective environmental conditions. Thermoacidophiles are challenged by pyroglutamate, a lactam that is spontaneously formed by cyclization of glutamate under aerobic thermoacidophilic conditions. It is known that growth of the thermoacidophilic crenarchaeonSaccharolobus solfataricus(formerlySulfolobus solfataricus) is completely inhibited by pyroglutamate. In the present study, we investigated the effect of pyroglutamate on the growth ofS. solfataricusand the closely related crenarchaeonSulfolobus acidocaldarius.In contrast toS. solfataricus,S. acidocaldariuswas successfully cultivated with pyroglutamate as a sole carbon source. Bioinformatical analyses showed that both members of theSulfolobaceaehave at least one candidate for a 5-oxoprolinase, which catalyses the ATP-dependent conversion of pyroglutamate to glutamate. InS. solfataricus, we observed the intracellular accumulation of pyroglutamate and crude cell extract assays showed a less effective degradation of pyroglutamate. Apparently,S. acidocaldariusseems to be less versatile regarding carbohydrates and prefers peptidolytic growth compared toS. solfataricus. Concludingly,S. acidocaldariusexhibits a more efficient utilization of pyroglutamate and is not inhibited by this compound, making it a better candidate for applications with glutamate-containing media at high temperatures.