Zuckerberg Institute for Water Research, Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Midreshet Ben Gurion 84990, Israel.
Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Ueberlandstrasse 133, 8600 Dübendorf, Switzerland.
Sci Rep. 2017 Feb 6;7:42068. doi: 10.1038/srep42068.
Production of public goods in biological systems is often a collaborative effort that may be detrimental to the producers. It is therefore sustainable only if a small fraction of the population shoulders the cost while the majority reap the benefits. We modelled this scenario using Escherichia coli populations producing colicins, an antibiotic that kills producer cells' close relatives. Colicin expression is a costly trait, and it has been proposed that only a small fraction of the population actively expresses the antibiotic. Colicinogenic populations were followed at the single-cell level using time-lapse microscopy, and showed two distinct, albeit dynamic, subpopulations: the majority silenced colicin expression, while a small fraction of elongated, slow-growing cells formed colicin-expressing hotspots, placing a significant burden on expressers. Moreover, monitoring lineages of individual colicinogenic cells showed stochastic switching between expressers and non-expressers. Hence, colicin expressers may be engaged in risk-reducing strategies-or bet-hedging-as they balance the cost of colicin production with the need to repel competitors. To test the bet-hedging strategy in colicin-mediated interactions, competitions between colicin-sensitive and producer cells were simulated using a numerical model, demonstrating a finely balanced expression range that is essential to sustaining the colicinogenic population.
生物系统中的公共产品生产通常是一种协作努力，这可能对生产者不利。因此，只有一小部分人口承担成本，而大多数人受益，这种情况才是可持续的。我们使用产生大肠杆菌素的大肠杆菌种群模拟了这种情况，大肠杆菌素是一种杀死生产者细胞近亲的抗生素。大肠杆菌素的表达是一种代价高昂的特征，有人提出只有一小部分人口积极表达抗生素。使用延时显微镜在单细胞水平上跟踪大肠杆菌素产生种群，显示出两个截然不同但动态的亚群：大多数沉默了大肠杆菌素的表达，而一小部分伸长、生长缓慢的细胞形成了大肠杆菌素表达的热点，给表达者带来了巨大的负担。此外，监测单个大肠杆菌素产生细胞的谱系表明，表达者和非表达者之间存在随机切换。因此，大肠杆菌素表达者可能参与了风险降低策略——即押注分散——因为他们需要平衡大肠杆菌素生产的成本与击退竞争者的需求。为了在大肠杆菌素介导的相互作用中检验押注分散策略，我们使用数值模型模拟了大肠杆菌素敏感细胞和生产者细胞之间的竞争，证明了一个精细平衡的表达范围对于维持大肠杆菌素产生种群至关重要。
