Effects of growth conditions on production of methyl selenides in cultures of Rhodobacter sphaeroides
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2.4.1 exposed to selenate or selenite produced volatile selenium compounds. Total amounts of dimethyl selenide, dimethyl diselenide, dimethyl sulfide and dimethyl disulfide in culture medium and headspace were determined. The highest selenate volatilization occurred in the late stationary phase of growth. However, cultures deprived of light in the stationary phase of growth produced much less of the volatile organo-selenium compounds. Lower culture pHs increased the rate of selenium volatilization. Low sulfate concentration limited biomass production and selenium volatilization; high sulfate concentrations had an enhancing effect on the release of organo-selenium compounds. Cultures of R. sphaeroides reacted very differently to amendments with increasing amounts of selenate and selenite. Only small amounts of selenite were volatilized; meanwhile high amounts of methylated selenides were found in selenate-poisoned cultures.
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