Microbial populations often experience fluctuations in nutrient complexity in their natural environment such as between high molecular weight polysaccharides and simple monosaccharides. However, it is unclear if cells can adopt growth behaviors that allow individuals to optimally respond to differences in nutrient complexity. Here, we directly control nutrient complexity and use quantitative single-cell analysis to study the growth dynamics of individuals within populations of the aquatic bacterium Caulobacter crescentus. We show that cells form clonal microcolonies when growing on the polysaccharide xylan, which is abundant in nature and degraded using extracellular cell-linked enzymes; and disperse to solitary growth modes when the corresponding monosaccharide xylose becomes available or nutrients are exhausted. We find that the cellular density required to achieve maximal growth rates is four-fold higher on xylan than on xylose, indicating that aggregating is advantageous on polysaccharides. When collectives on xylan are transitioned to xylose, cells start dispersing, indicating that colony formation is no longer beneficial and solitary behaviors might serve to reduce intercellular competition. Our study demonstrates that cells can dynamically tune their behaviors when nutrient complexity fluctuates, elucidates the quantitative advantages of distinct growth behaviors for individual cells and indicates why collective growth modes are prevalent in microbial populations.

微生物种群在其自然环境中经常经历营养复杂性的波动，例如在高分子量多糖和简单单糖之间。然而，尚不清楚细胞是否可以采取生长行为，使个体能够对营养复杂性的差异做出最佳反应。在这里，我们直接控制营养复杂性并使用定量单细胞分析来研究水生细菌Caulobacter crescentus种群中个体的生长动态. 我们表明，细胞在多糖木聚糖上生长时会形成克隆微集落，这种木聚糖在自然界中含量丰富，并被细胞外细胞连接酶降解；当相应的单糖木糖变得可用或养分耗尽时分散到单独生长模式。我们发现，在木聚糖上实现最大生长速率所需的细胞密度是木糖上的四倍，这表明聚集对多糖有利。当木聚糖上的集体转变为木糖时，细胞开始分散，表明菌落形成不再有益，单独的行为可能有助于减少细胞间的竞争。我们的研究表明，当营养复杂性波动时，细胞可以动态调整其行为，