Photoassimilation of acetate and the biosynthesis of amino acids by Chlorobium thiosulphatophilum

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Abstract
Growth of C. thiosulphatophilum was increased by the addition of low concentrations of acetate to the basal thiosulphate medium. Uptake of radioactive acetate by resting cell suspensions required the presence of bicarbonate and a source of reducing power such as H2 gas. Acetate was incorporated into all the major cell fractions in resting cell suspensions and in growing cultures. Poly-[beta]-hydroxybutyrate was not detected in C. thiosulphatophilum under conditions in which it was readily isolated from Rhodospirillum rubrum and Rhodomicrobium vannielii. Both [1-C14]acetate and [2-C14]acetate were incorporated into most of the amino-acids of the cell proteins. Radioactive amino-acids were isolated and decarboxylated; with the exception of leucine and isoleucine, there was very little radioactivity in the carboxyl groups. Alanine, aspartic-acid and glutamic-acid were degraded completely. The isotope distributions in alanine and aspartic-acid were similar to those in R. rubrum and Clostridium kluyveri. Phenylalanine was partially degraded and it was established that both [1-C14]acetate and [2-C14] acetate were incorporated into the aromatic ring.
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