on the Permeability of Thiobacillus Neapolitan Us to Thiosulphate

Abstract

Freshly prepared cells of T. neapolitanus had an effective thiosulphate-impermeable volume of 2·21 ml/g dry weight; on treatment of the bacteria with n-butanol this value fell to O· 86 ml/g dry weight. T. neapolitanus catalysed an exchange of sulphur between sulphite and the inner-sulphur group of thiosulphate although the bacteria appeared to be impermeable to sulphite. The exchange reaction was inhibited by N-ethylmaleimide and iodoacetamide. No accumulation of the substrate or products within the bacterial cell occurred during the oxidation of thiosulphate. It is concluded that thiosulphate sulphur enters the bacterial cell by a process other than simple diffusion and that the exchange between sulphite and thiosulphate takes place at the bacterial cell membrane. A possible role of sulphenyl derivatives in the uptake of thiosulphate is discussed.