Complete assimilation of cysteine by a newly isolated non-sulfur purple bacterium resembling Rhodovulum sulfidophilum (Rhodobacter sulfidophilus) |
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Authors: | Silke Heising Waltraud Dilling S Schnell B Schink |
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Institution: | Fakult?t für Biologie, Universit?t Konstanz, Postfach 5560, D-78434 Konstanz, Germany Tel. +49-7531-88–2140; Fax +49-7531-88-2966 e-mail: bernhard.schink@uni-konstanz.de, DE
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Abstract: | A rod-shaped, motile, phototrophic bacterium, strain SiCys, was enriched and isolated from a marine microbial mat, with cysteine
as sole substrate. During phototrophic anaerobic growth with cysteine, sulfide was produced as an intermediate, which was
subsequently oxidized to sulfate. The molar growth yield with cysteine was 103 g mol–1, in accordance with complete assimilation of electrons from the carbon and the sulfur moiety into cell material. Growth yields
with alanine and serine were proportionally lower. Thiosulfate, sulfide, hydrogen, and several organic compounds were used
as electron donors in the light, whereas cystine, sulfite, or elemental sulfur did not support phototrophic anaerobic growth.
Aerobic growth in the dark was possible with fructose as substrate. Cultures of strain SiCys were yellowish-brown in color
and contained bacteriochlorophyll a, spheroidene, spheroidenone, and OH-spheroidene as major photosynthetic pigments. Taking the morphology, photosynthetic pigments,
aerobic growth in the dark, and utilization of sulfide for phototrophic growth into account, strain SiCys was assigned to
the genus Rhodovulum (formerly Rhodobacter) and tentatively classified as a strain of R. sulfidophilum. In cell-free extracts in the presence of pyridoxal phosphate, cysteine was converted to pyruvate and sulfide, which is characteristic
for cysteine desulfhydrase activity (l-cystathionine γ-lyase, EC 4.4.1.1).
Received: 15 December 1995 / Accepted: 1 April 1996 |
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Keywords: | Cysteine Phototrophic bacteria Anaerobic degradation Non-sulfur purple bacteria Rhodovulum (Rhodobacter) sulfidophilum Microbial mats |
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