Energetics of end product excretion in anaerboic bacteria and the metabolism of fatty acids by Syntrophomonas wolfei
Anaerobic syntrophic bacteria degrade fatty acids which are important intermediates in anaerobic degradation and methanogenesis. These bacteria grow very slowly and require the presence of a hydrogen/formate-using organism to degrade fatty acids. Thus, these bacteria serve as models to study the biochemical aspects of mutualism and the energetics of slow growing organisms. We developed methods to physically separate cells of the anaerobic, fatty acid degrader, Syntrophomonas wolfei, from cells of the hydrogen user by Percoll gradient centrifugation and to selectively lyse S. wolfei cells using lysozyme. These methods allowed the study of the physiology of S. wolfei without significant contamination by cellular components of the hydrogen user. We also obtained pure cultures of S. wolfei by adapting the organism to grow on crotonate. Fatty acids were degraded by the {beta}-oxidation pathway using a coenzyme A (CoA) transferase activity to activate the fatty acid and substrate-level phosphorylation reactions to synthesize adenosine-5{prime}-triphosphate (ATP). The substrate specificity of the CoA transferase activity in the pure culture of S. wolfei differed from that found in the coculture suggesting that the ability to use crotonate resulted from an alteration of this enzyme. S. wolfei grown alone degraded crotonate in a manner similar to that of other crotonate-fermenting anaerobes, but the molar growth yields of S. wolfei were 2 to 3 times higher than those organisms. This suggests that the reduction of crotonyl-CoA to butyryl-CoA is energy yielding. S. wolfei contained a c-type cytochrome which may be involved in this reaction. S. wolfei synthesized large amounts of the storage polymer, poly-{beta}-hydroxybutyrate (PHB). Radioisotopic incorporation experiments showed that PHB was synthesized directly from the {beta}-oxidation intermediate rather than from the condensation of two acetyl-CoA molecules.
- Research Organization:
- Oklahoma Univ., Norman, OK (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AS05-83ER13053
- OSTI ID:
- 7013135
- Report Number(s):
- DOE/ER/13053-8; ON: DE90007549
- Country of Publication:
- United States
- Language:
- English
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