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Pseudomonas fluorescens subsp. cellulosa: an alternative model for bacterial cellulase.
G P Hazlewood1, J I Laurie, L M Ferreira
1Department of Biochemistry, AFRC Institute of Animal Physiology & Genetics Research, Babraham, Cambridge, UK.
The Journal of Applied Bacteriology
|March 1, 1992
Summary
Pseudomonas fluorescens subsp. cellulosa secretes cellulase and xylanase enzymes that are induced by plant fibers but repressed by sugars. This soil bacterium
Area of Science:
- Microbiology
- Biochemistry
- Enzymology
Background:
- Pseudomonas fluorescens subsp. cellulosa is a Gram-negative soil bacterium.
- It utilizes crystalline cellulose and xylan as primary carbon and energy sources.
- Enzyme synthesis is regulated by specific inducers and repressors.
Purpose of the Study:
- To investigate the cellulase and xylanase enzyme system of Pseudomonas fluorescens subsp. cellulosa.
- To compare its system with established models for cellulolytic anaerobes.
Main Methods:
- Bacterial cultivation with various carbon sources.
- Enzyme activity assays in culture supernatant and bound fractions.
- Western blotting to detect specific enzymes.
Main Results:
- Enzyme synthesis is induced by cellulose/xylan and repressed by simple sugars.
- Enzymes are secreted and do not associate with the cell surface.
- Significant enzyme activity binds to insoluble cellulose.
- Endoglucanase B, xylanase A, and cellodextrinase are synthesized and likely glycosylated.
Conclusions:
- The cellulase/hemicellulase system of Pseudomonas fluorescens subsp. cellulosa is distinct from that of anaerobic bacteria.
- Enzymes are secreted extracellularly and bind to insoluble substrates.
- Post-translational modification, possibly glycosylation, occurs.