What We Can Deduce about Metabolism in the Moderate Halophile Chromohalobacter Salexigens from its Genomic Sequence

Role of Central Metabolism in the Osmoadaptation of the Halophilic Bacterium Chromohalobacter salexigens

“…However, the gene for this enzyme from Propionibacterium freudenreichii can only complement fructose-1,6-bisphosphatase (fbp) mutations but not phosphofructokinase (pfkA/pfkB) mutations in Escherichia coli (37), indicating that it functions in the gluconeogenic direction but not in the glycolytic direction. Significantly, the analysis of the C. salexigens genome also failed to identify a clear-cut representative of a fructose bisphosphatase (19), raising the possibility that Csal1534, which has been annotated as Ppi-Pfk, may be a fructose bisphosphatase.…”

“…Typically, microorganisms using the ED pathway lack glycolytic enzyme(s), such as Pfk (34,35). In fact, unambiguous annotation of the gene encoding Pfk in C. salexigens has been difficult (19). There are five ORFs annotated in the JGI website (genome.ornl.gov) as potential phosphofructokinases, although they have low homology with bona fide Pfks (supplemental Fig.…”

“…The above results reflect that osmoadaptation in C. salexigens has implications on metabolic performance. C. salexigens genome has been automatically annotated, and preliminary analyses (16,19) and a first genome-based metabolic reconstruction (18) have been published. To further understand the interplay between osmoadaptation and metabolism, we critically assessed a number of routes in this metabolic network related to central metabolism, with emphasis on the pathways leading to precursors of ectoines, as well as to metabolites found in supernatants.…”

“…This is a key enzyme as it links the TCA cycle with the first enzyme of the ectoines synthesis pathway (aspartokinase). C. salexigens has only one aspartokinase catalyzing the formation of aspartyl phosphate, which is a common metabolic intermediate in the biosynthesis of ectoines and aspartate family of amino acids (8,19). For a complete description of the in silico analysis, see supplemental Table S1 and Figs.…”

“…There are two major pathways for the catabolism of sugars to pyruvate: glycolysis (Embden-Meyerhof pathway) (EM) 8 and the Entner-Doudoroff (ED) pathway (17). The physiological relevance of these pathways for the growth of C. salexigens is not known (16,18,19). The synthesis of ectoines consumes acetyl-CoA, which is produced by oxidative decarboxylation of pyruvate, and oxaloacetate (OAA), which is an intermediate in the TCA cycle and has to be replenished by anaplerotic pathways (16).…”