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Two genes encoding the beta-galactosidase of Lactobacillus sake
M Obst1, E R Meding, R F Vogel
1Institut für Lebensmitteltechnologie, Stuttgart, Germany.
Microbiology (Reading, England)
|December 1, 1995
Summary
The genes lacL and lacM from Lactobacillus sake encode a functional beta-galactosidase. These genes can be used in food-grade vectors for Lactobacillus species.
Area of Science:
- Microbiology
- Molecular Biology
- Enzymology
Background:
- Lactobacillus sake DSM 20017 possesses a chromosomal beta-galactosidase.
- The enzyme is crucial for lactose metabolism in certain bacteria.
Purpose of the Study:
- To clone and characterize the genes encoding Lactobacillus sake beta-galactosidase.
- To investigate the potential application of these genes in biotechnology.
Main Methods:
- Gene cloning into Escherichia coli using vector pRB473.
- Deletion analysis to determine gene function.
- Transcriptional analysis and protein homology studies.
- Phenotypic expression in heterologous hosts.
Main Results:
- The beta-galactosidase is encoded by two genes, lacL and lacM, on an 8.65 kbp fragment.
- Both lacL and lacM are essential for enzyme activity and are co-transcribed.
- The L. sake beta-galactosidase shows low homology to other known beta-galactosidases, but shares conserved residues suggesting a common origin.
- The enzyme was successfully expressed in E. coli and Lactobacillus curvatus.
Conclusions:
- The lacL and lacM genes provide a functional beta-galactosidase.
- These genes are suitable for developing food-grade vectors and alpha-complementation systems for meat lactobacilli.
- Potential to replace antibiotic resistance markers in genetic engineering of lactic acid bacteria.