Glucose transport system in a facultative iron-oxidizing bacterium, Thiobacillus ferrooxidans

Abstract

Properties of a heat-labile glucose transport system in Thiobacillusferrooxidans strain AP-44 were investigated with iron-grown cells. [14C]glucose was incorporated into ceil fractions, and the cells metabolized [14C]glucose to 14CO2. Amytal, rotenone, cyanide, azide, 2,4-dinitrophenol, and dicyclohexylcarbodiimide strongly inhibited [14C]glucose uptake activity, suggesting the presence of an energy-dependent glucose transport system in T. ferrooxidans. Heavy metals, such as mercury, silver, uranium, and molybdate, markedly inhibited the transport activity at 1 mM. When grown on mixotrophic medium, the bacteria preferentially utilized ferrous iron as an energy source. When iron was exhausted, the cells used glucose if the concentration of ferrous sulfate in the medium was higher than 3% (wt/vol). However, when ferrous sulfate was lower than 1%, both of the energy sources were consumed simultaneously.

Mixotrophic Growth of a Thiobacillus ferrooxidans Strain

“…This is due to the very close association between an obligately heterotrophic bacterium, Acidiphilium cryptum, and T. ferrooxidans in supposedly pure cultures (1, 4). Recently, Sugio et al (8) reported the isolation of a facultative iron-oxidizing T. ferrooxidans strain which was able to utilize glucose and grow on an organic medium without iron. However, the culture used by Sugio et al (8) has been shown to be impure and was a mixture of heterotrophic A. cryptum (70 mol% guanine plus cytosine [G+C] content) and an obligately autotrophic T. ferrooxidans (57 mol% G+C) (A. Harrison, Division of Biological Sciences, University of Missouri, Columbia, Mo., personal communication).…”