Membrane-associated Sulfur Oxidation by the Autotroph Thiobacillus thiooxidans

Abstract

associated sulfur oxidation by the autotroph Thiobacillus thiooxidans. J. Bacteriol. 92:899-904. 1966.-Washed cell wall-membrane fragments derived from sulfur-grown cells of the strictly autotrophic bacterium, Thiobacillus thiooxidans, oxidized elemental sulfur to sulfate without the addition of cofactors. The oxidation was optimal at pH 7.0 and was increased by the presence of wetting agents. Oxygen uptake was inhibited by cyanide, azide, and thiol-binding agents. Sulfite was also oxidized, and both the sulfurand sulfite-oxidizing systems were heat-labile. Neither thiosulfate nor tetrathionate was oxidized by soluble or membrane preparations. The fragments fixed C402 in the presence of ribose-5-phosphate, Mg++, and adenosine triphosphate. Sulfur oxidation did not provide energy for C1402 fixation in this system.

Energy conservation in acidophilic bacteria.

“…3A) and with sulfite oxidation in mitochondria, we suggest that 4>H+ in acidophilic thiobacilli may well be generated as illustrated in Fig. 3B and C. These latter mechanisms may be especially applicable to Thiobacillus thiooxidans since membrane preparations of this organism oxidize both sulfur and sulfite by azide-sensitive pathways (1). Although other mechanisms could have been proposed (23), those illustrated possess an extreme feature; the half reactions are arranged such that H+ produced by the oxidation of sulfur compounds are released outside the cell, and cytochrome oxidase consumes H+ within the cell to maintain the internal pH close to neutrality.…”

“…Thiobacillus thiooxidans grows between the pH values 1.0 and 4.0 with an optimum at pH 2.5 (113) and uses elemental sulfur or reduced sulfur compounds as substrates (1,73,108,134). Thio-bacillus thiooxidans is an obligate chemoautotroph.…”

“…The internal pH of chemoautotrophic acidophiles is close to neutrality and furthermore is independent of external pH (1,16,30,33,34,113,119). Relatively few measurements of ApH have been made (Table 2).…”

Is Fe3+/2+ cycling an intermediate in sulphur oxidation by Fe2+-grown Thiobacillus ferrooxidans

“…The acceleration in the rate may be attributed, at least in part, to the time course of cell attachment to the S ~ particles. This acceleration is stimulated by the detergent Tween 80 [8].…”

The reductive reactions of Thiobacillus ferrooxidans on sulphur and selenium

“…Growth of the cells used herein was in a chemostat such that the sole energy source was from the oxidation of Fe z+ by 02. Under these conditions a constitutive sulphur oxidising system is present [2,3]. In this paper we report that T. ferrooxidans produces H2S from elemental sulphur under both anaerobic and aerobic conditions.…”