UPTAKE OF AMINOPTERIN BY BACILLUS SUBTILIS

Abstract

B. subtilis strain ATCC 6051 contains an active trans port system for concentrating aminopterin-2-Cl4. Growth inhibition by the drug and part of its uptake can be prevented or reversed by the pyrimidine moiety of thiamine. The cellular disposition of aminopterin is heterogeneous; part of the uptake is metabolically inactive, and components of uptake differ in their ability to be eluted. Below pH 4.5 an additional uptake insensitive to the pyrimidine appears. Aminopterin-resistant mutants of B. subtilis are essentially lacking in the pyrimidine-sensitive uptake of the parent. The uptake system is dependent on Fe+++ and an energy supply, and persists in protoplast preparations.