Long-term social dynamics drive loss of function in pathogenic bacteria

Area of Science:

• Microbiology
• Evolutionary Biology
• Pathogen Dynamics

Background:

• Social interactions drive bacterial evolution in lab settings, but relevance to natural infections is unclear.
• Interpreting bacterial changes during infection as host adaptation overlooks social dynamics.
• Sophisticated methods track bacterial changes, but adaptive explanations are lacking.

Purpose of the Study:

• To investigate if social interactions drive long-term behavioral changes in bacterial pathogens during infection.
• To understand the evolutionary pressures on Pseudomonas aeruginosa during cystic fibrosis lung infections.
• To challenge the assumption that bacterial trait loss during infection is solely host-driven.

Main Methods:

• Longitudinal monitoring of phenotypic and genotypic dynamics in Pseudomonas aeruginosa from patient samples.
• Analysis of bacterial social behaviors, specifically iron acquisition via siderophore production and uptake.
• Sequence analysis to generate hypotheses about selection pressures driving observed changes.

Main Results:

• Pseudomonas aeruginosa loses cooperative siderophore production during lung infections.
• Bacteria retain the ability to utilize siderophores produced by others even after losing production capability.
• Loss of the siderophore uptake receptor occurs only after cooperative producers are eliminated from the population.

Conclusions:

• Social competition, not just host adaptation, significantly drives bacterial evolution during infection.
• Loss of function in pathogens may reflect social dynamics rather than host environment adaptation.
• Sequence analysis can generate testable hypotheses for in situ bacterial evolution.