Growth of Chlorobium Limicola F. Thiosulfatophilum on Polysulfides

Abstract

Elemental sulfur is commonly found as an intermediate product in the oxidation of sulfide by green and purple bacteria. In the early tog phase, when growing on sulfide, batch cultures of these anoxygenic phototrophic bacteria have a milky appearance due to the often massive accumulation of elemental sulfur, either stored intracellulary (Chromatiaceae) or extracellularly (Chlorobiaceae and Ectothiorhodospiraceae). The amount of sulfur decreases after sulfide depletion, since its oxidation to sulfate continues, whereas its formation from sulfide has stopped. However, in some species sulfur oxidation does not start before the sulfide supply is exhausted (Truper, 1978). In batch cultures of Chromatium vinosum it has been observed that, prior to sulfide depletion, the specific content of sulfur (mmol mg protein-1) shows little variation (van Gemerden, 1968, 1984). The maximum specific content of sulfur in different species of purple sulfur bacteria is very similar, i e, 30–35% of the ash-free dry weight (van Niel, 1931; Triiper and Schlegel, 1964; van Gemerden, 1968; lias and van Gemerden, 1987). Chlorobium species have been much less studied in this respect, but generally marine species deposit less sulfur than fresh water strains do. The accumulation of elemental sulfur is the result of the nature of the initial substrate, but the specific content of sulfur is very much influenced by the growth rate.