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Evidence for plasmid-associated lactose metabolism inLactobacillus casei subsp.casei.
B M Chassy1, E M Gibson, A Guiffrida
1Microbiology Section, Laboratory of Microbiology and Immunology, National Institute of Dental Research, National Institutes of Health, 20014, Bethesda, Maryland, USA.
Current Microbiology
|January 23, 2013
Summary
Researchers induced lactose-negative variants in Lactobacillus casei DR1002 using chemical agents. These variants lacked the pDR101 plasmid, indicating lactose metabolism is plasmid-mediated in this bacterium.
Area of Science:
- Microbiology
- Molecular Biology
- Bacteriology
Background:
- Lactose fermentation is crucial for many bacterial species, including Lactobacillus casei.
- Understanding the genetic basis of metabolic traits like lactose fermentation is essential for microbial research and applications.
Purpose of the Study:
- To investigate the genetic basis of lactose fermentation in Lactobacillus casei subsp. casei DR1002.
- To determine if lactose metabolism is plasmid-mediated in Lactobacillus casei DR1002.
Main Methods:
- Induction of lactose-negative (Lac-) variants using chemical mutagens: acriflavin, ethidium bromide, and mitomycin C.
- Culturing and selection of Lac- variants through successive transfers.
- Plasmid analysis using cesium chloride-ethidium bromide isopycnic gradient ultracentrifugation.
Main Results:
- Chemical treatments resulted in a near 100% loss of lactose fermentation in Lactobacillus casei DR1002.
- Cesium chloride-ethidium bromide ultracentrifugation revealed the consistent absence of the 23-mdal plasmid (pDR101) in Lac- clones.
Conclusions:
- Lactose metabolism in Lactobacillus casei DR1002 is mediated by a plasmid, specifically the pDR101 plasmid.
- This finding is analogous to lactose metabolism in lactic streptococci, suggesting a conserved genetic mechanism.
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