, 2001). This ED pathway, in which the phosphorylation step is postponed, is also probably used by the other members of the carbohydrate-utilizing group. In this pathway, glucose is oxidized via gluconate to 2-keto-3-deoxygluconate and then phosphorylated to 2-keto-3-deoxy-6-phosphogluconate, Alectinib which is further split into pyruvate and glyceraldehyde-3-phosphate (Tomlinson
et al., 1974). In addition, other steps in common metabolic pathways may have special modifications in the halophilic Archaea, such as the production of acetate by an ADP-forming acetyl-CoA synthetase (Siebers & Schönheit, 2005). Halobacterium does not grow on sugars, but its growth is stimulated by the addition of carbohydrates to the medium (Oren, 2002b), where
glucose can be transformed into gluconate (Sonawat et al., 1990). Oxidation of carbohydrates is often incomplete and is usually associated with the production of acids (Hochstein, 1978). In the presence of glycerol, some species of the genus Haloferax and Haloarcula produce selleck inhibitor acetate, pyruvate, and d-lactate (Oren & Gurevich, 1994). Production of d-lactate, acetate, and pyruvate from glycerol by the haloarchaeal communities of the Dead Sea and saltern crystallization ponds has also been observed. In these environments, acetate is poorly utilized (Oren, 1995). Analysis of the genome of the flat square archaeon Etofibrate Hqr. walsbyi showed a few unique features. One of them is the presence of a gene cluster that allows uptake of phosphonates and subsequent cleavage of the carbon–phosphorus bond by a phosphonate lyase. Another is the possible use of dihydroxyacetone as a carbon and energy source after its uptake via a phosphoenol pyruvate-dependent phosphotransferase system (Bolhuis et al., 2006). Growth studies showed that, indeed, Hqr. walsbyi could metabolize dihydroxyacetone (Elevi Bardavid & Oren, 2008). Based
on the analysis of its genome, this species can also grow on pyruvate and glycerol (Bolhuis et al., 2006). Its apparent inability to take up glycerol, as shown in an analysis of the natural community in a saltern crystallizer pond in Mallorca (Rosselló-Mora et al., 2003) remains unexplained. A food chain is thus possible, in which glycerol produced as an osmotic solute by the alga Dunaliella is converted in part to dihydroxyacetone by extremely halophilic bacteria of the genus Salinibacter (Bacteroidetes). Haloquadratum and other members of the Halobacteriaceae (Elevi Bardavid & Oren, 2008; Elevi Bardavid et al., 2008) can then take up the dihydroxyacetone and the remainder of the glycerol. Some representatives of the family can metabolize aliphatic and aromatic hydrocarbons and long-chain fatty acids, such as hexadecanoic acid (Bertrand et al., 1990; Oren, 2006; McGenity, 2010a).