A bacterium (strain TJ330) capable of using carbon disulphide (CS2) as its sole energy source in an acidic environment was isolated from a peat biofilter used in experiments to remove CS2 and hydrogen sulphide (H2S) from air. Its physiology and taxonomy are described here. The strain oxidized CS2, H2S and elemental sulphur to sulphate chemolithotrophically. The rate of sulphate production was highest at pH 2. The maximum growth rate constant (micromax) using CS2 as a substrate was 3.9 x 10(-2) h(-1) (generation time 18 h) and the Monod constant (Ks) was 0.97-2.6 micromol l(-1) CS2 (74-198 microg l(-1)), corresponding to an equilibrium with 15-40 ppm CS2 in the headspace. The optimum growth temperature using elemental sulphur as a substrate was 28 degrees C. The strain bears morphological and physiological similarities to Thiobacillus thiooxidans, but the latter is incapable of oxidizing CS2. The strain TJ330 (DSM 8985) showed only 44.2 + 11.8% DNA homology with the type strain T. thiooxidans ATCC 19377, while its homology with T. ferrooxidans ATCC 23270 was 17.1 + 3.4%. The strain TJ 330 represents a high-affinity bacterium which can effectively remove low CS2 concentrations in an acid environment. These properties can be utilized in biotechnological purification applications.