Sodium ion-stimulated α-[1-14C]aminoisobutyric acid uptake in alkalophilic Bacillus species

Abstract

Alkalophilic bacillus no. 8-1 grows well in alkaline media containing 2.5 to 5% NaCl. The uptake of α-aminoisobutyric acid (AIB) into the cells is stimulated by the addition of NaCl (Na+) up to a concentration of 0.2 M, but other monovalent cations such as K+, Li+, or NH4+ cannot substitute for Na+. The kinetic studies reveal that, when Na+ concentration increases from 0.02 to 0.2 M in alkaline medium, the Km for transport decreases, whereas Vmax remains almost constant. Competition studies indicate that glycine, L-alanine, L-serine, and AIB share common carriers for the transport of the compounds into cells. Other alkalophilic bacteria are also found to require Na+ for uptake of AIB into the cells.