Early Developmental Program Shapes Colony Morphology in Bacteria

• Highly ordered spatiotemporal events occur during bacterial colony development
• Colony typically initiates by formation of leading-cell chains arranged in a Y shape
• Y-arm extension defines the size and the shape of the future colony
• A mutant in the phosphodiesterase ymdB displays aberrant developmental patterns

SummaryWhen grown on a solid surface, bacteria form highly organized colonies, yet little is known about the earliest stages of colony establishment. Following Bacillus subtilis colony development from a single progenitor cell, a sequence of highly ordered spatiotemporal events was revealed. Colony was initiated by the formation of leading-cell chains, deriving from the colony center and extending in multiple directions, typically in a “Y-shaped” structure. By eradicating particular cells during these early stages, we could influence the shape of the resulting colony and demonstrate that Y-arm extension defines colony size. A mutant in ymdB encoding a phosphodiesterase displayed unordered developmental patterns, indicating a role in guiding these initial events. Finally, we provide evidence that intercellular nanotubes contribute to proper colony formation. In summary, we reveal a “construction plan” for building a colony and provide the initial molecular basis for this process.

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