The ithree institute, University of Technology Sydney, Ultimo, NSW 2007, Australia.
Proc Natl Acad Sci U S A. 2013 Jul 9;110(28):11541-6. doi: 10.1073/pnas.1218898110. Epub 2013 Jun 24.
Twitching motility-mediated biofilm expansion is a complex, multicellular behavior that enables the active colonization of surfaces by many species of bacteria. In this study we have explored the emergence of intricate network patterns of interconnected trails that form in actively expanding biofilms of Pseudomonas aeruginosa. We have used high-resolution, phase-contrast time-lapse microscopy and developed sophisticated computer vision algorithms to track and analyze individual cell movements during expansion of P. aeruginosa biofilms. We have also used atomic force microscopy to examine the topography of the substrate underneath the expanding biofilm. Our analyses reveal that at the leading edge of the biofilm, highly coherent groups of bacteria migrate across the surface of the semisolid media and in doing so create furrows along which following cells preferentially migrate. This leads to the emergence of a network of trails that guide mass transit toward the leading edges of the biofilm. We have also determined that extracellular DNA (eDNA) facilitates efficient traffic flow throughout the furrow network by maintaining coherent cell alignments, thereby avoiding traffic jams and ensuring an efficient supply of cells to the migrating front. Our analyses reveal that eDNA also coordinates the movements of cells in the leading edge vanguard rafts and is required for the assembly of cells into the "bulldozer" aggregates that forge the interconnecting furrows. Our observations have revealed that large-scale self-organization of cells in actively expanding biofilms of P. aeruginosa occurs through construction of an intricate network of furrows that is facilitated by eDNA.
抽搐运动介导的生物膜扩展是一种复杂的、多细胞的行为，使许多种细菌能够主动定殖于表面。在这项研究中，我们探索了铜绿假单胞菌活跃扩展生物膜中形成的复杂互联轨迹网络模式的出现。我们使用高分辨率、相差时程显微镜并开发了复杂的计算机视觉算法，以跟踪和分析扩展生物膜期间单个细胞的运动。我们还使用原子力显微镜检查了扩展生物膜下基底的形貌。我们的分析表明，在生物膜的前沿，高度协调的细菌群体会在半固体培养基表面迁移，并在此过程中沿沟槽形成，随后的细胞更倾向于沿这些沟槽迁移。这导致了网络轨迹的出现，这些轨迹引导着物质向生物膜的前沿运输。我们还确定了细胞外 DNA (eDNA) 通过保持细胞的一致性排列，促进了沟道网络中的有效物质流动，从而避免了交通堵塞，并确保了对迁移前沿的细胞的有效供应。我们的分析表明，eDNA 还协调了前沿先锋筏细胞的运动，并需要将细胞组装成“推土器”聚集体，以形成互联的沟槽。我们的观察结果表明，铜绿假单胞菌活跃扩展生物膜中细胞的大规模自组织是通过 eDNA 促进的复杂沟槽网络的构建来实现的。
