Department of Microbiology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
ISME J. 2024 Jan 8;18(1). doi: 10.1093/ismejo/wrae199.
Cooperative behaviours in human, animal, and even microbial societies are vulnerable to exploitation. Kin discrimination has been hypothesized to help stabilize cooperation. However, the mechanisms that sustain cooperative behaviour remain poorly understood. Here, we investigate the role of kin discrimination in limiting the spread of cheats in adjoining populations during surfactant-dependent cooperative swarming over surfaces using the bacterium Bacillus subtilis as a model organism. We show that mixing surfactant secreting cooperators and cheats that do not produce surfactants at 1:1 initial ratio quickly leads to cooperation collapse. However, when such common swarms encounter nonkin B. subtilis swarms, the proportion of the surfactant nonproducers decreases, suggesting that kinship dependent interactions may limit cheats' advantage in an adjoining population. To further validate this finding, we subjected wild-type cooperators to multiple transient encounters with kin and nonkin swarms over 20 cycles of experimental evolution. The evolved populations exposed to nonkin swarms less frequently contained defective swarming phenotypes compared to those encountering kin swarms. Altogether, our results support the prediction that the spread of cheats in an adjoining bacterial population is impeded by kin discrimination interactions, which might have a role in stabilizing cooperative behaviour in evolving populations.
人类、动物，甚至微生物社会中的合作行为很容易受到利用。亲缘识别被假设有助于稳定合作。然而，维持合作行为的机制仍未被很好地理解。在这里，我们使用枯草芽孢杆菌作为模型生物，研究了亲缘识别在限制表面活性剂依赖的合作群体扩散过程中相邻种群中骗子传播的作用。我们表明，以 1:1 的初始比例混合分泌表面活性剂的合作者和不产生表面活性剂的骗子会迅速导致合作崩溃。然而，当这些常见的群体遇到非亲缘关系的枯草芽孢杆菌群体时，表面活性剂非生产者的比例会下降，这表明亲缘关系相关的相互作用可能会限制骗子在相邻种群中的优势。为了进一步验证这一发现，我们让野生型合作者在 20 个实验进化循环中多次与亲缘关系和非亲缘关系的群体进行短暂接触。与遇到亲缘关系群体的进化群体相比，暴露于非亲缘关系群体的进化群体中缺陷型群体扩散表型的频率较低。总的来说，我们的结果支持了这样一种预测，即在相邻细菌种群中骗子的传播受到亲缘识别相互作用的阻碍，这可能在进化种群中稳定合作行为方面发挥作用。
