Örmälä-Odegrip Anni-Maria, Ojala Ville, Hiltunen Teppo, Zhang Ji, Bamford Jaana K H, Laakso Jouni
Centre of Excellence in Biological Interactions, Department of Biological and Environmental, University of Jyväskylä, P.O. Box, 35, 40014, Jyväskylä, Finland.
Department of Biosciences, University of Helsinki, P.O. Box 65, 00014, Helsinki, Finland.
BMC Evol Biol. 2015 May 7;15:81. doi: 10.1186/s12862-015-0341-1.
Consumer-resource interactions constitute one of the most common types of interspecific antagonistic interaction. In natural communities, complex species interactions are likely to affect the outcomes of reciprocal co-evolution between consumers and their resource species. Individuals face multiple enemies simultaneously, and consequently they need to adapt to several different types of enemy pressures. In this study, we assessed how protist predation affects the susceptibility of bacterial populations to infection by viral parasites, and whether there is an associated cost of defence on the competitive ability of the bacteria. As a study system we used Serratia marcescens and its lytic bacteriophage, along with two bacteriovorous protists with distinct feeding modes: Tetrahymena thermophila (particle feeder) and Acanthamoeba castellanii (surface feeder). The results were further confirmed with another study system with Pseudomonas and Tetrahymena thermophila.
We found that selection by protist predators lowered the susceptibility to infections by lytic phages in Serratia and Pseudomonas. In Serratia, concurrent selection by phages and protists led to lowered susceptibility to phage infections and this effect was independent from whether the bacteria shared a co-evolutionary history with the phage population or not. Bacteria that had evolved with phages were overall more susceptible to phage infection (compared to bacteria with history with multiple enemies) but they were less vulnerable to the phages they had co-evolved with than ancestral phages. Selection by bacterial enemies was costly in general and was seen as a lowered fitness in absence of phages, measured as a biomass yield.
Our results show the significance of multiple species interactions on pairwise consumer-resource interaction, and suggest potential overlap in defending against predatory and parasitic enemies in microbial consumer-resource communities. Ultimately, our results could have larger scale effects on eco-evolutionary community dynamics.
消费者 - 资源相互作用是种间拮抗相互作用中最常见的类型之一。在自然群落中，复杂的物种相互作用可能会影响消费者与其资源物种之间相互协同进化的结果。个体同时面临多个敌人，因此它们需要适应几种不同类型的天敌压力。在本研究中，我们评估了原生生物捕食如何影响细菌群体对病毒寄生虫感染的易感性，以及细菌的防御是否会对其竞争能力产生相关成本。作为研究系统，我们使用了粘质沙雷氏菌及其裂解性噬菌体，以及两种具有不同摄食模式的食细菌原生生物：嗜热四膜虫（颗粒捕食者）和卡氏棘阿米巴（表面捕食者）。另一组以铜绿假单胞菌和嗜热四膜虫为研究系统的实验进一步证实了该结果。
我们发现，原生生物捕食者的选择降低了粘质沙雷氏菌和铜绿假单胞菌对裂解性噬菌体感染的易感性。在粘质沙雷氏菌中，噬菌体和原生生物的同时选择导致对噬菌体感染的易感性降低，并且这种效应与细菌是否与噬菌体群体具有共同进化历史无关。与具有多种敌人进化历史的细菌相比，与噬菌体共同进化的细菌总体上更容易受到噬菌体感染，但它们对与其共同进化的噬菌体的易感性低于原始噬菌体。一般来说，细菌敌人的选择是有代价的，在没有噬菌体的情况下，以生物量产量衡量，这表现为适应性降低。
我们的结果表明了多种物种相互作用对成对消费者 - 资源相互作用的重要性，并表明在微生物消费者 - 资源群落中，抵御捕食性和寄生性敌人的防御机制可能存在潜在重叠。最终，我们的结果可能会对生态进化群落动态产生更大规模的影响。
