Oxidative Stickland reactions in an obligate aerobic organism – amino acid catabolism in the Crenarchaeon Sulfolobus solfataricus

Abstract

The thermoacidophilic Crenarchaeon Sulfolobus solfataricus is a model organism for archaeal adaptation to extreme environments and renowned for its ability to degrade a broad variety of substrates. It has been well characterised concerning the utilisation of numerous carbohydrates as carbon source. However, its amino acid metabolism, especially the degradation of single amino acids, is not as well understood. In this work, we performed metabolic modelling as well as metabolome, transcriptome and proteome analysis on cells grown on caseinhydrolysate as carbon source in order to draw a comprehensive picture of amino acid metabolism in S. solfataricus P2. We found that 10 out of 16 detectable amino acids are imported from the growth medium. Overall, uptake of glutamate, methionine, leucine, phenylalanine and isoleucine was the highest of all observed amino acids. Our simulations predict an incomplete degradation of leucine and tyrosine to organic acids, and in accordance with this, we detected the export of branched‐chain and aromatic organic acids as well as amino acids, ammonium and trehalose into the culture supernatants. The branched‐chain amino acids as well as phenylalanine and tyrosine are degraded to organic acids via oxidative Stickland reactions. Such reactions are known for prokaryotes capable of anaerobic growth, but so far have never been observed in an obligate aerobe. Also, 3‐methyl‐2‐butenoate and 2‐methyl‐2‐butenoate are for the first time found as products of modified Stickland reactions for the degradation of branched‐chain amino acids. This work presents the first detailed description of branched‐chain and aromatic amino acid catabolism in S. solfataricus.

Early Response of Sulfolobus acidocaldarius to Nutrient Limitation

“…Although we observed major changes at the transcript and protein levels, the overlap between both data sets was low. In previous studies in S. solfataricus where we analyzed the effect of growth on different carbon sources we observed a rather specific response with a good overlap between both data sets (Wolf et al, 2016; Stark et al, 2017). However, also from other studies as for example in Thermoplasma thermophilus (Sun et al, 2010), there is evidence that the response to stress conditions is much more complex and different levels of post-transcriptional and post-translational modification are involved.…”

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

“…For further investigation of the predicted 5-oxoprolinases, we looked at differences in transcription of the gene candidates that could explain the observed phenotypes. Therefore, we analysed published transcriptome data of both members of the Sulfolobaceae on different substrates [26–29]. The relative expression levels compared to the median of the whole transcriptome were compared to the presence of glutamate (and accordingly pyroglutamate) in the medium and is shown in Table 3.…”

“…Although the culture conditions and medium composition differed among the studies, we found a noticeable correlation between the presence of glutamate in the medium and an enhanced expression (up to 5-fold) of the 5-oxoprolinase candidates in S. acidocaldarius [27–29]. Contrastingly, the expression of all gene candidates in S. solfataricus was remarkably low and did not increase when glutamate was present in the medium [26].…”

Sulfolobus – A Potential Key Organism in Future Biotechnology

“…The different Sulfolobus strains differ significantly in their metabolic potential. S. solfataricus possesses a broad substrate specificity and uses various sugars such as polysaccharides (e.g., cellulose, starch, dextrin), disaccharides (e.g., maltose and sucrose), hexoses (e.g., D -glucose, D -galactose, D -mannose, and L -fucose), pentoses (e.g., D -arabinose, L -arabinose, D -xylose), aldehydes, alcohols (e.g., ethanol, phenol), sugar acids as well as tryptone, peptides, and amino acids as carbon source ( Grogan, 1989 ; Izzo et al, 2005 ; Brouns et al, 2006 ; Joshua et al, 2011 ; Comte et al, 2013 ; Wolf et al, 2016 ; Stark et al, 2017 ). For S. solfataricus , a genome scale model comprising 718 metabolic and 58 transport/exchange reactions and 705 metabolites was used to simulate growth on 35 different carbon sources ( Ulas et al, 2012 ).…”

“…In general, the availability of genome scale models, functional genomics, and systems biology approaches for Sulfolobales under different stress and growth conditions in combination with biochemical and genetic studies enabled an in depth insight into metabolism and cellular processes [e.g., growth on L -fucose and casamino acids compared to D -glucose in S. solfataricus ( Wolf et al, 2016 ; Stark et al, 2017 )]. The established knowledge forms an important prerequisite for the establishment of Sulfolobus spp.…”