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Characterization of the Highly Autolytic Lactococcus lactis subsp. cremoris Strains CO and 2250
Applied and Environmental Microbiology
|March 15, 2006
Summary
Autolytic Lactococcus lactis strains showed maximum cell lysis with limited glucose. The acmA gene was confirmed to play a role in cell separation and lysis in these bacteria.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Autolysis is a crucial process in bacterial cell wall metabolism.
- Lactococcus lactis subsp. cremoris strains exhibit significant autolytic activity, impacting their technological applications.
- Understanding the factors influencing autolysis is key to controlling bacterial behavior.
Purpose of the Study:
- To investigate the autolytic properties of two Lactococcus lactis subsp. cremoris strains, CO and 2250.
- To identify the optimal conditions for inducing autolysis in these strains.
- To characterize the autolytic enzymes involved and confirm the role of the acmA gene.
Main Methods:
- Culturing Lactococcus lactis subsp. cremoris strains under varying glucose concentrations, pH, and temperatures.
- Extracting autolysins from cell wall fractions using SDS, guanidine hydrochloride, and lithium chloride.
- Analyzing enzyme activity via renaturing SDS-polyacrylamide gel electrophoresis with Micrococcus luteus or L. lactis subsp. cremoris CO as substrates.
- Confirming gene presence using Southern hybridization and analyzing acmA deletion mutants.
Main Results:
- Maximum lysis occurred in M17 broth with limited glucose (0.4-0.5%); excess glucose or lactose/galactose reduced lysis.
- Autolysis was prevented by excess glucose, but sodium fluoride addition induced lysis in L. lactis subsp. cremoris CO.
- Autolysins were extracted, with a major lytic band of 48 kDa observed for strain CO, suggesting multiple autolytic enzymes.
- The acmA gene was present in both strains and its deletion mutant confirmed its role in cell separation and lysis.
Conclusions:
- Autolysis in Lactococcus lactis subsp. cremoris is significantly influenced by glucose availability.
- At least two distinct autolytic enzymes are present in these strains.
- The acmA gene is essential for proper cell separation and contributes to the autolytic process in Lactococcus lactis.
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