Metabolism of halophilic archaea

In spite of their common hypersaline environment, halophilic archaea are surprisingly different in their nutritional demands and metabolic pathways. The metabolic diversity of halophilic archaea was investigated at the genomic level through systematic metabolic reconstruction and comparative analysis of four completely sequenced species: Halobacterium salinarum, Haloarcula marismortui, Haloquadratum walsbyi, and the haloalkaliphile Natronomonas pharaonis. The comparative study reveals different sets of enzyme genes amongst halophilic archaea, e.g. in glycerol degradation, pentose metabolism, and folate synthesis. The carefully assessed metabolic data represent a reliable resource for future system biology approaches as it also links to current experimental data on (halo)archaea from the literature

Biosynthetic pathways in Methanospirillum hungatei as determined by 13C nuclear magnetic resonance

The main metabolic pathways in Methanospirillum hungatei GP1 were followed by using 13C nuclear magnetic resonance, with 13C-labeled acetate and CO2 as carbon sources. The labeling patterns found in carbohydrates, amino acids, lipids, and nucleosides were consistent with the formation of pyruvate from acetate and CO2 as the first step in biosynthesis. Carbohydrates are formed by the glucogenic pathway, and no scrambling of label was observed, indicating that the oxidative or reductive pentose phosphate pathways are not functioning at significant rates. The pathways for amino acid biosynthesis are the usual ones, with the exception of that for isoleucine. The tricarboxylic acid pathway is incomplete and operates in a reductive direction to form alpha-ketoglutarate. The phytanyl chains of lipids are synthesized from acetate via mevalonic acid.</jats:p

Biosynthetic pathways in Methanospirillum hungatei as determined by 13C nuclear magnetic resonance.

The main metabolic pathways in Methanospirillum hungatei GP1 were followed by using 13C nuclear magnetic resonance, with 13C-labeled acetate and CO2 as carbon sources. The labeling patterns found in carbohydrates, amino acids, lipids, and nucleosides were consistent with the formation of pyruvate from acetate and CO2 as the first step in biosynthesis. Carbohydrates are formed by the glucogenic pathway, and no scrambling of label was observed, indicating that the oxidative or reductive pentose phosphate pathways are not functioning at significant rates. The pathways for amino acid biosynthesis are the usual ones, with the exception of that for isoleucine. The tricarboxylic acid pathway is incomplete and operates in a reductive direction to form alpha-ketoglutarate. The phytanyl chains of lipids are synthesized from acetate via mevalonic acid