Spatial Organization of Expanding Bacterial Colonies Is Affected by Contact-Dependent Growth Inhibition

Area of Science:

• Microbial Ecology
• Bacterial Competition
• Systems Biology

Background:

• Microbial communities significantly impact human health and the environment.
• Bacteria utilize toxin delivery systems, like contact-dependent inhibition (CDI), to manipulate community composition.
• The role of CDI systems in spatially structured bacterial populations requires further investigation.

Purpose of the Study:

• To compare the impact of different CDI systems on bacterial populations at single-cell and population levels.
• To identify key drivers of CDI-mediated competition in spatially structured bacterial populations.
• To understand how distinct CDI systems differentially affect bacterial population composition and spatial arrangement.

Main Methods:

• Utilized an iterative approach combining experimental studies with an Escherichia coli system.
• Employed computational modeling to analyze CDI system effects.
• Assessed CDI impacts at both single-cell and population scales within spatially structured colonies.

Main Results:

• CDI systems exhibit subtle, system-specific effects at the single-cell level, forming boundaries between inhibitor and target cells.
• CDI systems significantly impede the range expansion of susceptible target cells during colony growth.
• Inoculum density, speed of inhibition, and biological cost of CDI are critical drivers of competition; toxin magnitude has minimal impact.

Conclusions:

• CDI systems play a crucial role in shaping bacterial community structure and spatial organization.
• The specific characteristics of CDI systems, rather than just toxin potency, determine their competitive outcomes.
• Understanding CDI mechanisms provides insights into microbial interactions and ecosystem dynamics.