Spatial proximity dictates bacterial competition and expansion in microbial communities

Area of Science:

• Microbiology
• Ecology
• Systems Biology

Background:

• Bacterial interactions (inhibition/facilitation) shape microbial communities by altering shared environments.
• Most interaction studies neglect spatial effects, focusing on well-mixed conditions.
• Understanding spatial dynamics is critical for microbial ecology and infection.

Purpose of the Study:

• To investigate how spatial structure influences bacterial interactions and community expansion under antibiotic stress.
• To identify and characterize novel facilitation mechanisms in spatially structured microbial communities.

Main Methods:

• Utilized a combination of experimental evolution and mathematical modeling.
• Focused on interactions between immotile Klebsiella pneumoniae and motile Pseudomonas aeruginosa in the presence of a β-lactam antibiotic.
• Analyzed bacterial spread and community dynamics at millimeter scales.

Main Results:

• A spatial facilitation mechanism was identified where Klebsiella pneumoniae degrades antibiotics, enabling Pseudomonas aeruginosa expansion.
• Klebsiella pneumoniae is initially essential but ultimately suppressed to a minority, acting as a hidden initiator.
• This facilitation was observed at millimeter scales and in more complex communities, including a clinical isolate.

Conclusions:

• Spatially explicit experiments are essential for uncovering certain bacterial facilitation mechanisms.
• Findings have implications for understanding biofilms, polymicrobial infections, and antibiotic resistance.
• The study highlights the importance of spatial context in microbial community dynamics and evolution.