Data from: The physical boundaries of public goods cooperation between surface-attached bacterial cells

Bacteria secrete a variety of compounds important for nutrient scavenging, competition mediation and infection establishment. While there is a general consensus that secreted compounds can be shared and therefore have social consequences for the bacterial collective, we know little about the physical limits of such bacterial social interactions. Here, we address this issue by studying the sharing of iron-scavenging siderophores between surface-attached microcolonies of the bacterium Pseudomonas aeruginosa. Using single-cell fluorescence microscopy, we show that siderophores, secreted by producers, quickly reach non-producers within a range of 100 µm, and significantly boost their fitness. Producers in turn respond to variation in sharing efficiency by adjusting their pyoverdine investment levels. These social effects wane with larger cell-to-cell distances and on hard surfaces. Thus, our findings reveal the boundaries of compound sharing, and show that sharing is particularly relevant between nearby yet physically separated bacteria on soft surfaces, matching realistic natural conditions such as those encountered in soft tissue infections.

细菌可分泌多种对养分摄取、竞争调控及感染定植至关重要的化合物。尽管学界普遍认为分泌的化合物可被共享，进而对细菌群落产生社会性影响，但我们对这类细菌社会互动的物理边界仍知之甚少。本研究以铜绿假单胞菌（Pseudomonas aeruginosa）表面附着的微菌落为研究对象，探讨其相互间的夺铁型铁载体（iron-scavenging siderophores）共享现象，以此解决上述问题。借助单细胞荧光显微镜（single-cell fluorescence microscopy），我们发现由产生菌分泌的铁载体可在100微米范围内快速扩散至非产生菌，并显著提升其适合度。产生菌亦可根据共享效率的差异，调整其对脓菌素（pyoverdine）的投入水平以作出响应。这类社会性影响会随细胞间距增大以及在硬质表面环境中逐渐减弱。因此，本研究揭示了化合物共享的边界条件，并证实共享现象在软质表面上、彼此邻近但物理分离的细菌之间尤为显著，这与软组织感染等真实自然环境中的情况相符。