The sulfur metabolism of Cytophaga johnsonae
Because the cellular sulfur of most bacteria is essentially reduced sulfur form, the energetically expensive process of assimilatory sulfate reduction is prevented by various regulatory mechanisms when reduced sulfur is available. However, members of the Cytophaga-Flexibacter group of gliding bacteria contain 20% or more of their sulfur in the form of the sulfonate moiety of sulfonolipids, which is derived from cysteate; thus a large portion of their cellular sulfur is only one step more reduced than sulfate. Regulation of sulfate assimilation by Cytophaga johnsonae differs from that in other bacteria studied in that, when reduced sulfur sources such as a low concentration of cystine or a peptide-containing medium are available, the initial steps of sulfate assimilation that lead to cysteate, and thus sulfonolipid synthesis are operative, whereas the terminal steps of sulfate assimilation leading to cysteine and methionine (reduced sulfur) synthesis are repressed. The biosynthetic pathway leading to cysteate has not yet been elucidated. Cysteate sulfur can be derived from either sulfate or cystine, but the origin of the carbon is an enigma. It appears that cysteate carbon arises from a glycolytic intermediate. In a series of experiments with cell-free extracts, no evidence was obtained for the participation of phosphoenolpyruvate as a precursor to cysteate. Two lines of evidence support the hypothesis that phosphoserine is the ultimate precursor to cysteate: (a) this pathway does not require the existence of sulfonate intermediates (none have ever been detected), and (b) addition of phosphoserine to a cell extract incubated with ({sup 35}S)cysteine stimulated the incorporation of {sup 35}S into cysteate.
- Research Organization:
- Connecticut Univ., Storrs, CT (United States)
- OSTI ID:
- 5613695
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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IDENTIFICATION OF ORGANIC SULPHUR COMPOUNDS FORMED DURING THIOSULPHATE OXIDATION BY THIOBACILLUS THIORPARUS
Related Subjects
CYSTINE
BIOSYNTHESIS
METHIONINE
SULFATE-REDUCING BACTERIA
METABOLISM
SULFATES
BIOLOGICAL PATHWAYS
SULFUR 35
TRACER TECHNIQUES
AMINO ACIDS
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
DAYS LIVING RADIOISOTOPES
DISULFIDES
DRUGS
EVEN-ODD NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LIPOTROPIC FACTORS
MICROORGANISMS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
RADIOISOTOPES
SULFUR COMPOUNDS
SULFUR ISOTOPES
SYNTHESIS
550501* - Metabolism- Tracer Techniques
550701 - Microbiology- Tracer Techniques