Bacterial growth in multicellular aggregates leads to the emergence of complex lifecycles

In response to environmental stresses such as starvation, many bacteria facultatively aggregate into multicellular structures that can attain new metabolic functions and behaviors. Despite the ubiquity and relevance of this form of collective behavior, we lack an understanding of how the spatiotemporal dynamics of aggregate development emerge from cellular physiology. Here, we study the development of multicellular aggregates by the marine bacterium Vibrio splendidus when it grows on the polysaccharide alginate. Transcriptional profiling was used to define genes differentially expressed at stages of aggregate morphogenesis, and between cell sub-populations, which included genes encoding a putative type IV pillus and carbon storage granules. Combined with measurements of in situ cellular physiology, we show that the coupling between growth and spatial gradient formation leads to the emergence of a complex lifecycle. Comparison of samples taken from early and late stages of aggregate development. Late stage taken after structures rupture, and represents 'shell' and released inner 'core' contents.为应对饥饿等环境胁迫，诸多细菌会发生兼性聚集，形成可获得全新代谢功能与行为模式的多细胞结构。尽管这种集体行为形式普遍存在且具有重要研究意义，但目前我们仍未能阐明聚集发育的时空动态是如何由细胞生理学过程催生而来的。本研究针对在多糖藻酸盐表面生长的海洋细菌灿烂弧菌（Vibrio splendidus）的多细胞聚集发育过程展开研究，通过转录谱分析（Transcriptional profiling）鉴定了聚集形态发生不同阶段以及不同细胞亚群间的差异表达基因，其中包含编码推定IV型菌毛（type IV pillus）与碳储存颗粒的基因。结合原位细胞生理学检测结果，我们证实生长与空间梯度形成的耦合作用可催生复杂生命周期的形成。我们对聚集发育早期与晚期的样本进行了对比分析，晚期样本采集自结构破裂之后，涵盖了‘外壳’以及释放出的内部‘核心’内容物。