Swarming and complex pattern formation in Paenibacillus vortex studied by imaging and tracking cells

Area of Science:

• Microbiology
• Bacterial Motility
• Colony Formation

Background:

• Swarming motility enables rapid microbial surface translocation.
• Paenibacillus vortex, a Gram-positive bacterium, displays advanced cooperative motility, forming intricate colonies sensitive to environmental cues.
• The cellular mechanisms driving this complex multicellular organization remain poorly understood.

Purpose of the Study:

• To investigate the cellular mechanisms of swarming motility in Paenibacillus vortex.
• To understand the formation of complex colonial patterns and multicellular organization.

Main Methods:

• Real-time light microscopy and in situ scanning electron microscopy were employed.
• Tracking antibiotic-resistant cells within sensitive colonies elucidated cell movement dynamics.
• Mitomycin C was used to induce filamentation for detailed swarming analysis.

Main Results:

• Paenibacillus vortex is peritrichously flagellated and swarms across a wide range of agar concentrations.
• Swarming cells form reversible, flagella-mediated connections, creating rafts and exhibiting collision avoidance.
• Complex behaviors observed include rotating colonies, Petri dish-wide supercolonies, and cell exchange.

Conclusions:

• Paenibacillus vortex forms complex colonies with significant cell reflux and interaction.
• Cell shape, flagellation, aversion to fusion, and temporary cell connections are key to swarming and rotation.
• Vigorous vortex formation is a social phenomenon requiring multiple cells, offering the first detailed cellular-level examination of this bacterium's swarming behavior.