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Deoxyribonucleic Acid homology among lactic streptococci
1New Zealand Dairy Research Institute, Palmerston North, New Zealand.
Applied and Environmental Microbiology
|January 1, 1981
Summary
DNA homology studies reveal distinct groupings among lactic streptococci, with Streptococcus cremoris and Streptococcus lactis strains forming separate clusters. However, some Streptococcus lactis strains showed high similarity to S. cremoris, impacting starter culture selection.
Area of Science:
- Microbiology
- Molecular Biology
- Food Science
Background:
- Lactic streptococci are crucial for dairy fermentation.
- Accurate strain identification is vital for starter culture selection in cheesemaking.
- Deoxyribonucleic acid (DNA) homology provides a robust method for bacterial classification.
Purpose of the Study:
- To classify 45 strains of lactic streptococci using DNA homology.
- To compare the genetic relatedness of Streptococcus cremoris, Streptococcus lactis, and Streptococcus diacetylactis.
- To assess the genetic distinctiveness of Streptococcus thermophilus relative to other lactic streptococci.
Main Methods:
- DNA-DNA hybridization was employed to determine genetic relatedness.
- Reference strains of Streptococcus cremoris and Streptococcus lactis were used for comparison.
- Analysis focused on the percentage of common base sequences between strains.
Main Results:
- Streptococcus cremoris strains clustered together based on DNA homology.
- Streptococcus lactis strains formed a distinct group, with some exceptions showing high homology to S. cremoris.
- Streptococcus diacetylactis strains were indistinguishable from S. lactis strains.
- Most S. cremoris, S. lactis, and S. diacetylactis strains shared over 50% DNA base sequence homology.
- Streptococcus thermophilus strains exhibited minimal genetic relationship with the other studied lactic streptococci.
Conclusions:
- DNA homology supports the differentiation of S. cremoris and S. lactis, but highlights inter-species genetic overlap.
- S. diacetylactis appears closely related to S. lactis.
- Findings have implications for selecting robust and specific starter cultures for cheese production.
- S. thermophilus represents a genetically distinct group within the lactic streptococci.
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