Phage endolysins are adapted to specific hosts and are evolutionarily dynamic.

Area of Science:

• Microbiology
• Evolutionary Biology
• Biochemistry

Background:

• Bacteriophage endolysins degrade bacterial cell walls for viral replication.
• Endolysin diversity in phages infecting the same species is significant.
• The evolutionary implications of endolysin diversity remain underexplored.

Purpose of the Study:

• Investigate the evolutionary implications of phage endolysin diversity.
• Assess the fitness costs associated with endolysin gene exchange between phages.
• Explore the adaptive potential of endolysins in new phage/host environments.

Main Methods:

• Utilized CRISPR-Cas9 genome editing for genetic exchange of endolysin genes.
• Transferred endolysin genes between distinct lactococcal phage genomes.
• Analyzed fitness costs and adaptive mutations following gene exchange.

Main Results:

• Fitness costs of endolysin exchange were minimal within the same bacterial strain but increased between different strains/species.
• Endolysins were observed to undergo natural homologous recombination between coinfecting phages.
• Phage endolysins acquired adaptive mutations in new phage/host environments.

Conclusions:

• Phage endolysins exhibit significant evolvability, recombining and adapting to new environments.
• Evolution acts on functional modules like endolysins, explaining phage diversity and mosaicism.
• Engineered endolysins hold promise as novel antimicrobial agents.