Diverse interactions among species within bacterial colonies lead to intricate spatiotemporal dynamics, which can affect their growth and survival. Here, we describe the emergence of complex structures in a colony grown from mixtures of motile and non-motile bacterial species on a soft agar surface. Time-lapse imaging shows that non-motile bacteria 'hitchhike' on the motile bacteria as the latter migrate outward. The non-motile bacteria accumulate at the boundary of the colony and trigger an instability that leaves behind striking flower-like patterns. The mechanism of the front instability governing this pattern formation is elucidated by a mathematical model for the frictional motion of the colony interface, with friction depending on the local concentration of the non-motile species. A more elaborate two-dimensional phase-field model that explicitly accounts for the interplay between growth, mechanical stress from the motile species, and friction provided by the non-motile species, fully reproduces the observed flower-like patterns.

中文翻译：

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多物种细菌菌落中的花朵状图案

细菌菌落内物种之间的多种相互作用导致错综复杂的时空动态，可能会影响其生长和生存。在这里，我们描述了在软琼脂表面上由活动和非活动细菌物种的混合物生长的菌落中复杂结构的出现。延时成像显示，非运动细菌在运动细菌向外迁移时会“搭便车”。非运动细菌在菌落的边界处积聚并引发不稳定性，留下了醒目的花朵状图案。通过菌落界面摩擦运动的数学模型阐明了控制这种模式形成的前部不稳定性的机制，摩擦力取决于非运动性物种的局部浓度。