title: Effect of extreme salt concentrations on the physiology and biochemistry of Halobacteroides acetoethylicus.
abstract: Halobacteroides acetoethylicus grew in media with 6 to 20% NaCl and displayed optimal growth at 10% NaCl. When grown in medium with an [NaCl] of 1.7 M, the internal cytoplasmic [Na+] and [Cl-] were 0.92 and 1.2 M, respectively, while K+ and Mg2+ concentrations in cells were 0.24 and 0.02 M, respectively. Intracellular [Na+] was fourfold higher than intracellular [K+]. Since Na+ and Cl- ions were not excluded from the cell, the influence of high salt concentrations on key enzyme activities was investigated in crude cell extracts. Activities greater than 60% of the maximal activity of the following key catabolic enzymes occurred at the following [NaCl] ranges: glyceraldehyde-3-phosphate dehydrogenase, 1 to 2 M; alcohol dehydrogenase (NAD linked), 2 to 4 M; pyruvate dehydrogenase, 0.5 to 1 M; and hydrogenase (methyl viologen linked), 0.5 to 3 M. These studies support the hypothesis that obligately halophilic, anaerobic eubacteria adapt to extreme salt concentrations differently than do halophilic, aerobic eubacteria, because they do not produce osmoregulants or exclude Cl-. This study also demonstrated that these halophilic, anaerobic eubacteria have a physiological similarity to archaebacterial halophiles, since Na+ and Cl- are present in high concentrations and are required for enzymatic activity.
authors.affiliation: Michigan Biotechnology Institute, Lansing 48909.
authors.forename: S
authors.initials: S
authors.lastname: Rengpipat
authors.forename: S E
authors.initials: SE
authors.lastname: Lowe
authors.forename: J G
authors.initials: JG
authors.lastname: Zeikus
mesh_terms: D000426:Alcohol Dehydrogenase / Q000378:metabolism; D001421:Bacteria, Anaerobic / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D003470:Culture Media; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D006864:Hydrogenase / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*; D014882:Water-Electrolyte Balance
chemical_list: D003470:Culture Media; D011768:Pyruvate Dehydrogenase Complex; D012965:Sodium Chloride; D011189:Potassium Chloride; D010088:Oxidoreductases; D000426:Alcohol Dehydrogenase; D006864:Hydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases