title: Genomic studies on nitrogen metabolism in Halomonas boliviensis: metabolic pathway, biochemistry and evolution.
abstract: Halomonas boliviensis LC1(T)=DSM 15516(T) is a halophilic bacterium that copiously produces osmolytes and polyesters. The growth of H. boliviensis is restricted when glutamate or glutamine is not included in its culture medium. The concentration of glutamate in the medium can regulate the production of either osmolytes or polyesters. However, genomic studies on the nitrogen assimilation have not been performed on H. boliviensis and other members of the family Halomonadaceae. Glutamate metabolism in H. boliviensis was discerned based on genome sequence analysis. The genome sequences of other Halomonadaceae members revealed similar enzymes to those found in H. boliviensis. H. boliviensis and H. elongata DSM 2581(T) acquired distinct glutamate dehydrogenase genes through horizontal gene transfer from a different bacterium. Two alleles of glutamine synthetase could be found in H. boliviensis, one of which was obtained from a thermophilic archaeon via horizontal gene transfer. Two subunits of glutamate synthase were also present in H. boliviensis. The small β-subunit had a molecular weight of 52 kDa and was phylogenetically closely affiliated to proteins of other halomonads and Gammaproteobacteria. The large (161 kDa) α-subunit of the halomonads gathered in a separate phylogenetic group, hence glutamate synthase α-subunits of halomonads may be included a novel group of enzymes. Furthermore, putative enzymes obtained from the genome of H. boliviensis should permit complete glutamate metabolism. A similar metabolism should be followed by other halomonads. However, some phenotypic differences between halomonads, such as the ability to assimilate ammonia, resulted as a consequence of horizontal gene transfer. Each enzyme that forms part of the glutamate metabolism in prokaryotes evolved following a different pattern. Yet, most enzymes of halomonads diverged in phylogenetic clusters composed of Proteobacteria, as might be expected.
authors.affiliation: Center of Biotechnology, Faculty of Sciences and Technology, San Simon University, Cochabamba, Bolivia. Electronic address: a.balderrsu@gmail.com.
authors.forename: Andrea
authors.initials: A
authors.lastname: Balderrama-Subieta
authors.forename: Jorge
authors.initials: J
authors.lastname: Quillaguamán
mesh_terms: D005075:Biological Evolution; D023281:Genomics; D005969:Glutamate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism; D020632:Halomonas / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D009584:Nitrogen / Q000378:metabolism*; D010802:Phylogeny
chemical_list: D018698:Glutamic Acid; D005969:Glutamate Dehydrogenase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
keywords: Glutamate metabolism; Halomonadaceae; Halomonas boliviensis; Halophilic bacteria