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Xylose uptake by the ruminal bacterium Selenomonas ruminantium
1Department of Microbiology, University of Georgia, Athens 30602.
Applied and Environmental Microbiology
|June 1, 1990
Summary
Selenomonas ruminantium HD4 utilizes an inducible xylose uptake system, likely involving a binding protein and permease. This process is energy-dependent and sensitive to protonophores and certain inhibitors, suggesting a complex transport mechanism.
Area of Science:
- Microbiology
- Bacterial Physiology
- Carbohydrate Metabolism
Background:
- Selenomonas ruminantium HD4 is a key ruminal bacterium involved in carbohydrate fermentation.
- Understanding xylose transport is crucial for elucidating its role in the rumen ecosystem.
Purpose of the Study:
- To investigate the mechanism of xylose uptake in Selenomonas ruminantium HD4.
- To determine if the phosphoenolpyruvate phosphotransferase system (PTS) is involved in xylose transport.
Main Methods:
- Whole-cell uptake assays using radiolabeled xylose.
- Inhibition studies with various metabolic inhibitors, protonophores, and cations.
- Kinetic analysis of xylose uptake.
- Fermentation product analysis.
Main Results:
- Xylose uptake was inducible and not mediated by the PTS.
- Uptake was inhibited by protonophores (CCCP, DNP, SF6847) and metabolic inhibitors (HgCl2, o-phenanthroline, Na-arsenate), suggesting energy dependence.
- Nonlinear uptake kinetics indicated potential involvement of multiple transport systems or proteins.
- Phenolic monomers inhibited xylose uptake and growth.
- Lactate, acetate, and propionate were major fermentation products.
Conclusions:
- Selenomonas ruminantium HD4 employs an active, energy-dependent xylose transport system, likely involving a binding protein and permease.
- The transport mechanism is distinct from the PTS and is sensitive to environmental factors like pH and phenolic compounds.