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Lysin production by phi C2(W), a prolate phage for Streptococcus lactis C2
Abstract:
A bacteriophage, phi C2(W), which attacked Streptococcus lactis strains C2, ML3 and 712, is described. It had a prolate head and non-contractile tail and produced large haloes around plaques. Infection of eight paired-strain cultures, each containing Str. lactis C2, with phi C2(W) resulted in marked inhibition of acid production for six cultures. Direct phage-nonhomologous "host' contact was not required for inhibition. Lysates of phi C2(W) contained a phage-induced lysin. Evidence is presented that the inhibitory effect of phi C2(W) against paired and multi-strain cultures is due to the lysis of phage-insensitive strains by phage lysin. An isometric phage, phi 712, was shown not to produce such a lysin.
Insights
Bacteriophage phi C2(W) inhibits Streptococcus lactis acid production by releasing a lysin that lyses insensitive strains. This phage-induced lysin is key to its inhibitory effect in mixed cultures.
Area of Science:
- Microbiology
- Bacteriophage research
- Dairy starter cultures
Background:
- Bacteriophages can impact starter culture performance in dairy fermentation.
- Understanding phage-host interactions is crucial for controlling fermentation processes.
Purpose of the Study:
- To characterize bacteriophage phi C2(W) and its effect on Streptococcus lactis.
- To investigate the mechanism behind phage-induced inhibition of acid production.
Main Methods:
- Morphological characterization of bacteriophage phi C2(W).
- Infection assays with paired and multi-strain cultures of Streptococcus lactis.
- Analysis of phage lysates for lytic activity.
Main Results:
- Bacteriophage phi C2(W) has a prolate head and non-contractile tail.
- phi C2(W) significantly inhibited acid production in most tested Streptococcus lactis cultures.
- Phage lysates contained a phage-induced lysin responsible for lysis of non-homologous strains.
Conclusions:
- The inhibitory effect of phi C2(W) is mediated by a phage-induced lysin.
- This lysin allows phi C2(W) to indirectly control phage-insensitive strains in mixed cultures.
- Bacteriophage phi 712 does not produce a similar lysin.