Department of Biochemistry, University of Zurich, Building Y27, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
Evolution. 2011 Jan;65(1):21-32. doi: 10.1111/j.1558-5646.2010.01121.x. Epub 2010 Oct 6.
Bacteria frequently exhibit cooperative behaviors but cooperative strains are vulnerable to invasion by cheater strains that reap the benefits of cooperation but do not perform the cooperative behavior themselves. Bacterial genomes often contain mobile genetic elements such as plasmids. When a gene for cooperative behavior exists on a plasmid, cheaters can be forced to cooperate by infection with this plasmid, rescuing cooperation in a population in which mutation or migration has allowed cheaters to arise. Here we introduce a second plasmid that does not code for cooperation and show that the social dilemma repeats itself at the plasmid level in both within-patch and metapopulation scenarios, and under various scenarios of plasmid incompatibility. Our results suggest that although plasmid carriage of cooperative genes can provide a transient defense against defection in structured environments, plasmid and chromosomal defection remain the only stable strategies in an unstructured environment. We discuss our results in the light of recent bioinformatic evidence that cooperative genes are overrepresented on mobile elements.
细菌经常表现出合作行为，但合作菌株容易受到骗子菌株的入侵，骗子菌株可以从合作中获益，但自己却不进行合作行为。细菌基因组通常包含可移动的遗传元件，如质粒。当质粒上存在合作行为的基因时，通过感染这种质粒，骗子可以被迫合作，从而挽救在突变或迁移允许骗子出现的种群中的合作。在这里，我们引入了第二个不编码合作行为的质粒，并表明在斑块内和集合种群情景下以及在各种质粒不兼容的情景下，质粒水平上的社会困境会重复出现。我们的结果表明，尽管质粒携带合作基因可以为结构环境中的缺陷提供暂时的防御，但在非结构环境中，质粒和染色体缺陷仍然是唯一稳定的策略。我们根据最近的生物信息学证据，即合作基因在移动元件上的过度表达，讨论了我们的结果。
