The evolution of specificity in evolving and coevolving antagonistic interactions between a bacteria and its phage

Area of Science:

• Evolutionary Biology
• Microbial Ecology
• Genetics

Background:

• Exploitative specificity evolves influenced by environmental variability and trade-offs.
• Coevolution, reciprocal adaptation between species, can shape host-parasite specificity patterns.

Purpose of the Study:

• To investigate the role of coevolution in the evolution of phage infectivity range.
• To examine the relationship between phage infectivity range and phage growth rate.
• To understand the impact of reciprocal selective pressures on within- and between-population strategies.

Main Methods:

• Utilized the bacterium Pseudomonas fluorescens SBW25 and its DNA phage Phi2.
• Compared phage evolution under coevolutionary conditions versus phage evolution alone.
• Analyzed phage infectivity range, growth rate, and genotype-by-genotype interactions.

Main Results:

• Coevolution led to broader phage infectivity range without reduced growth rate.
• Phage evolution without coevolution increased growth rate but not infectivity range.
• Coevolution induced within-population diversification into generalist and specialist phage types.
• Evidence of multilocus gene-for-gene interaction and a cost of broad infectivity range.
• Emergence of bacterial-phage genotype interactions affecting bacterial growth rate.

Conclusions:

• Coevolution drives the emergence of diverse phage strategies and specialization.
• Reciprocal selective pressures promote the coexistence of generalist and specialist phages.
• Coevolutionary dynamics are crucial for understanding the evolution of host-parasite interactions.