ELEMENTAL SULFUR PRODUCTION DURING MIXOTROPHIC GROWTH ON HYDROGEN ANDTHIOSULFATE OF THERMOPHILIC HYDROGEN-OXIDIZING BACTERIA

In this study we measured the exogenous production and the intracellul ar content of elemental sulfur (S0) in the thermophilic sulfur-oxidizi ng bacteria Hydrogenobacter spp. and Bacillus schlegelii during mixoli thoautotrophic growth on hydrogen and thiosulfate. Under these conditi ons, all strains produced and released white-yellow hydrophilic S0 par ticles into the growth medium. Hydrophilic S0 was separated from cells by a differential low-speed centrifugation procedure. The S0 pellets were dried, and the S0 was purified by column chromatography and by th in-layer chromatography (TLC). The S0 TLC-band could be stained with t riphenyltetrazolium chloride and piperidine procedure. Determination o f intracellular S0 content was performed from fresh cells absolutely f ree of exogenous S0 particles. Quantitation of S0 was performed by hig h-performance liquid chromatography, colorimetric thiocyanate procedur e, and by UV-spectra analyses. All the strains studied, in particular B. schlegelii strains, released significant quantities of S0 into the growth media. In contrast, the intracellular S0 content was very low. Significant rhodanese activity in the presence of thiosulfate was meas ured with toluene-permeabilized cells and cell-free extracts of B. sch legelii (type strain) and Hydrogenobacter spp. (strain T3).