Competition between Pseudomonas species constrains ecological diversification in polymicrobial biofilms

Area of Science:

• Microbial Ecology
• Evolutionary Biology
• Bacterial Genetics

Background:

• Polymicrobial biofilms are recognized as environments promoting bacterial evolution.
• The specific impact of interspecies interactions on adaptive processes within biofilms is not fully understood.

Purpose of the Study:

• To investigate the evolutionary dynamics of competing bacterial species within biofilms of varying complexity.
• To determine how interspecies interactions influence adaptation over time.

Main Methods:

• Utilized custom-engineered 3D-printed flow systems for biofilm cultivation over 18 days.
• Employed whole-population and whole-genome sequencing to analyze evolutionary changes.
• Conducted co-culture experiments with evolved bacterial strains.

Main Results:

• Pseudomonas defluvii exhibited significant diversification in simple biofilms but reduced variation in complex biofilms, indicating constrained adaptation.
• Pseudomonas brenneri showed minimal evolutionary changes regardless of biofilm complexity.
• Genomic analysis linked P. defluvii adaptation to biofilm regulation and chemotaxis.
• Evolved P. defluvii strains outperformed ancestral forms in co-culture, while P. brenneri remained stable.

Conclusions:

• Biofilm lifestyle generally promotes bacterial adaptation, but interspecies diversity can impose species-specific constraints on evolution.
• Interspecies interactions play a crucial role in shaping bacterial evolutionary trajectories within polymicrobial communities.
• Findings offer insights into bacterial evolution in complex environments, relevant to clinical and industrial microbiology.