Periodic phenomena in Proteus mirabilis swarm colony development

Area of Science:

• Microbiology
• Bacterial Morphogenesis
• Colony Development

Background:

• Proteus mirabilis exhibits complex, geometrically regular swarm colony patterns.
• Understanding the temporal and spatial regulation of bacterial swarming is crucial for microbiology.
• Previous studies have focused on the macroscopic patterns without fully detailing the underlying phases.

Purpose of the Study:

• To quantify periodic macroscopic events in Proteus mirabilis swarm colony morphogenesis.
• To investigate the influence of environmental factors on the distinct phases of colony development.
• To define quantifiable parameters for swarm colony development and identify regulatory mechanisms.

Main Methods:

• Utilized basic microbiological techniques and advanced imaging for macroscopic measurements.
• Distinguished and analyzed distinct phases: lag, swarming, and consolidation cycles.
• Manipulated bacterial growth and motility by altering medium composition (glucose and agar concentrations).

Main Results:

• Identified three initial phases followed by repeating swarming-consolidation cycles, with each terrace representing one cycle.
• Demonstrated that lag phase duration depends on inoculation density, suggesting cooperative and inhibitory effects.
• Observed internal waves in later swarm phases, resulting from organized bacterial cohorts; medium composition affects expansion kinetics and dynamics, not nutrient depletion.

Conclusions:

• Proteus mirabilis swarm colony development is a cyclical process regulated by density-dependent thresholds.
• Medium composition, particularly agar concentration, significantly alters colony expansion dynamics and phase durations.
• Terracing frequency is largely independent of factors affecting expansion, but cycle timing is influenced by temperature and enrichment.