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Tlie influence of various 0,-concentrations on chemoautotrophic growth was dcterniincd in thc range from microaerobic t o aerobic conditions. Chromatium vinosurn D, Thiocystis violacea 231 1 and Chromatiurn yracile 25-1 were grown chemoautotropliically using consecutively repeated batch riiltures. Rapid growth of all thrce strains occurred only under microaerobic conditions. Thc fastcst growth (1.c = 0.058) was obtained with Chromatium gracile 25-1 grown in the prcsence of 1 mg 0, . 1 -l. For optimal chemoautotrophic growth aulfur-containing cells had to bc supplied continuously with cxtracellular electron donor. Multiplication of Thiocystis violacea 231 1 and Chromatiwn gracile 25-1 was significantly inhibited after several cell generations, while Chromatiurn winosum D could be grown unlimited. I n case of the latter bacterium any given 0,-concentration determined il unique growth rate and a unique specific bclil a content. The analysis of absorption spect.ra of whole cclls revealed that different pigment complexes were regulated separately by oxygen. Growth yields were not dependent on the 0,-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 0,-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.

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Isolation and characterization of some chemoautotrophic Chromatiaceae CHAHLUTTE: KAMPF and N. PFENNIG (Ileceived M a y 26, 1986) Three strains of facultatively chemoautotrophic Chromatiaceae were isolated from natural habitats under chemotrophic conditions and identified as Chromatium gracile (strains 23-3 and 25-1) and T h i o c~p~a roseopersicina (strain LABOE). The strains utilized hydrogen and reduced sulfur compounds for photo-and chemolithosutotrophic growth. Ammonium or dinitrogen were utilized as nitrogcn sources for photo-and chemotrophic growth. With most of the organic carbon compounds examined chemoheterotrophic growth was dependend on thc presence of a reduced sulfur compound. The newly isolated strains grew chemoorganotrophically with fumarate, fructose as well as with some short-chain fatty acids and aliphatjc alcohols. The determination of the respiratory activity of Chromatium gracile 25-1 revealed that the utilization of butyrate for chemotrophic growth was not constitutive. The maximal respiratory activity of phototrophically grown Chromatium gracile 25-1 was 2 times higher than that of other facultative cliemotrophic Chromatiaceae. The respiratory activity of the obligately phototrophic Thiocapsa pfennigii was similar to that of phototrophically grown facultatively chemotrophic Chromatiaceae. 33'

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