Revisiting lactococcal abortive infection-like antiphage systems: diversity, structures, and mechanisms

Area of Science:

• Bacteriology
• Microbial Genetics
• Dairy Microbiology

Background:

• Lactococcus lactis and Lactococcus cremoris are crucial for dairy fermentation.
• These bacteria face constant phage infection in dairy environments.
• Abortive infection (Abi)-like systems are key bacterial defense mechanisms against phages.

Purpose of the Study:

• To review and analyze Lactococcus Abi-like antiphage systems.
• To examine their activity spectrum, lytic cycle interference, and mechanisms.
• To investigate the genomic location and evolutionary context of these systems.

Main Methods:

• Literature review and analysis of existing data on Abi-like systems.
• Examination of phage escape mutants for mechanistic insights.
• Structural superimposition and domain prediction for mechanism exploration.
• Comparative genomics of sequenced Lactococcus strains.

Main Results:

• Abi-like systems exhibit diverse antiphage activity and mechanisms.
• Phage escape mutants provide insights into Abi system function.
• Most characterized Abi-like systems are chromosomally encoded, not plasmid-borne.
• Lactococcus possesses a wide array of phage defense mechanisms.

Conclusions:

• Co-evolution with phages, driven by dairy applications, has equipped Lactococcus with numerous Abi-like defense systems.
• Understanding these systems is vital for robust dairy fermentation processes.
• Genomic location (chromosomal) is more common for these defense systems than previously thought.