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Cloning and Characterization of Two Closely Linked Cellulase Genes from Cellvibrio mixtus
1Department of Microbiology, University of Queensland, St. Lucia, 4072, Brisbane, Australia
Current Microbiology
|July 1, 1996
Summary
Researchers identified two genes in Cellvibrio mixtus responsible for breaking down cellulose and xylan. One gene (cmcI) degrades carboxymethylcellulose and xylan, while another (exoI) degrades microcrystalline cellulose (avicel).
Area of Science:
- Microbiology
- Enzymology
- Molecular Biology
Background:
- Cellvibrio mixtus produces enzymes capable of degrading various plant polysaccharides.
- Understanding the genetic basis of cellulase and xylanase production is crucial for biotechnological applications.
Purpose of the Study:
- To identify and characterize genes responsible for the hydrolysis of carboxymethylcellulose, xylan, and avicel in Cellvibrio mixtus.
- To investigate the genetic organization and expression of these enzyme-encoding genes.
Main Methods:
- Subcloning of a 16.5-kb BamHI fragment from Cellvibrio mixtus.
- Gene expression in Escherichia coli.
- Enzyme activity assays for carboxymethylcellulase, xylanase, and avicel hydrolysis.
- Northern blot analysis to determine gene transcription.
Main Results:
- A 2.7-kb fragment containing the cmcI gene encoded a 74 kDa enzyme degrading carboxymethylcellulose and xylan, but not avicel.
- A second cellulase gene, exoI, located 5.5 kb downstream of cmcI, produced 53.7 kDa and 51.5 kDa proteins and degraded avicel.
- Northern analysis indicated that cmcI and exoI are not co-transcribed in an operon.
Conclusions:
- Cellvibrio mixtus possesses distinct genes for the degradation of soluble and insoluble cellulose forms.
- The genes cmcI and exoI are independently regulated, suggesting differential control mechanisms for enzyme production.