title: NH4+ transport system of a psychrophilic marine bacterium, Vibrio sp. strain ABE-1.
abstract: NH4(+) transport system of a psychrophilic marine bacterium Vibrio sp. strain ABE-1 (Vibrio ABE-1) was examined by measuring the uptake of [14C]methylammonium ion (14CH3NH3+) into the intact cells. 14CH3NH3+ uptake was detected in cells grown in medium containing glutamate as the sole nitrogen source, but not in those grown in medium containing NH4Cl instead of glutamate. Vibrio ABE-1 did not utilize CH3NH3+ as a carbon or nitrogen source. NH4Cl and nonradiolabeled CH3NH3+ completely inhibited 14CH3NH3+ uptake. These results indicate that 14CH3NH3+ uptake in this bacterium is mediated via an NH4+ transport system and not by a specific carrier for CH3NH3+. The respiratory substrate succinate was required to drive 14CH3NH3+ uptake and the uptake was completely inhibited by KCN, indicating that the uptake was energy dependent. The electrochemical potentials of H+ and/or Na+ across membranes were suggested to be the driving forces for the transport system because the ionophores carbonylcyanide m-chlorophenylhydrazone and monensin strongly inhibited uptake activities at pH 6.5 and 8.5, respectively. Furthermore, KCl activated 14CH3NH3+ uptake. The 14CH3NH3+ uptake activity of Vibrio ABE-1 was markedly high at temperatures between 0 degrees and 15 degrees C, and the apparent Km value for CH3NH3+ of the uptake did not change significantly over the temperature range from 0 degrees to 25 degrees C. Thus, the NH4+ transport system of this bacterium was highly active at low temperatures.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Chou
authors.forename: T
authors.initials: T
authors.lastname: Matsunaga
authors.forename: Y
authors.initials: Y
authors.lastname: Takada
authors.forename: N
authors.initials: N
authors.lastname: Fukunaga
mesh_terms: D000643:Ammonium Chloride / Q000378:metabolism; D001692:Biological Transport; D002244:Carbon / Q000378:metabolism; D003470:Culture Media; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008744:Methylamines / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D013696:Temperature; D014733:Vibrio / Q000254:growth & development / Q000378:metabolism*
chemical_list: D003470:Culture Media; D008744:Methylamines; D000644:Quaternary Ammonium Compounds; D000643:Ammonium Chloride; D005973:Glutamine; D018698:Glutamic Acid; D002244:Carbon; C027451:methylamine; D009584:Nitrogen