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Multiple modification/restriction systems in lactic streptococci and their significance in defining a phage-typing
The Journal of Dairy Research
|October 1, 1980
Summary
Lactic streptococci utilize modification restriction (M/R) systems as a primary defense against phages. Understanding these systems is key to managing phage interactions in starter cultures.
Area of Science:
- Microbiology
- Bacteriology
- Virology
Background:
- Lactic streptococci are crucial in dairy fermentation.
- Bacteriophages (phages) pose a significant threat to lactic streptococci starter cultures.
- Understanding phage-host interactions is vital for industrial applications.
Purpose of the Study:
- To quantitatively analyze the interactions between lactic streptococci and their phages.
- To identify and characterize modification restriction (M/R) systems in lactic streptococci.
- To develop a model for predicting phage-bacteria interactions.
Main Methods:
- Quantitative analysis of 30 nonhomologous phage-bacteria reactions.
- Development and application of a mathematical model to identify M/R systems.
- Experimental validation using modified phages to confirm restriction mechanisms.
Main Results:
- 23 out of 30 nonhomologous reactions showed phage restriction by bacteria.
- A mathematical model identified at least 4-5 M/R systems, with up to 3 per strain.
- Mechanisms of restriction included limitations of detection, lysogeny, and unproven restriction.
Conclusions:
- Modification restriction (M/R) is a major defense mechanism of lactic streptococci against phages.
- Phage host range is not a reliable classification criterion due to M/R systems.
- These findings offer a rational basis for defining starter culture rotations to mitigate phage issues.