Chemoautotrophic growth of Thiocystis violacea, Chromatium gracile and C. vinosum in the dark at various O 2 ‐concentrations

The influence of various O 2 ‐concentrations on chemoautotrophic growth was determined in the range from microaerobic to aerobic conditions. Chromatium vinosum D, Thiocystis violacea 2311 and Chromatium gracile 25‐1 were grown chemoautotrophically using consecutively repeated batch cultures. Rapid growth of all three strains occurred only under microaerobic conditions. The fastest growth (μ = 0.058) was obtained with Chromatium gracile 25‐1 grown in the presence of 1 mg O 2 · 1 −1 . For optimal chemoautotrophic growth sulfur‐containing cells had to be supplied continuously with extracellular electron donor. Multiplication of thiocystis violacea 2311 and Chromatium gracile 25‐1 was significantly inhibited after several cell generations, while Chromatium vinosum D could be grown unlimited. In case of the latter bacterium any given O 2 ‐concentration determined a unique growth rate and a unique specific bchl α content. The analysis of absorption spectra of whole cells revealed that different pigment complexes were regulated separately by oxygen. Growth yields were not dependent on the O 2 ‐concentration. A growth yield of 12 g dry cell mass per mol of thiosulfate oxidized was determined for Chromatium vinosum D growing in the micro‐ to semiaerobic O 2 ‐concentration range. When compared to phototrophically grown cells, the catalase content of chemotrophically grown cells was 2 times lower while the maximal specific respiration rate of the cells was 7 times higher. The ecological significance of the kinetics of chemotrophic growth under various growth conditions is discussed.