Experimental evidence of a tripartite mutualism: bacteria protect ant fungus gardens from specialized parasites
Experimental evidence of a tripartite mutualism: bacteria protect ant fungus gardens from specialized parasites
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DOI：
10.1034/j.1600-0706.2003.12036.x
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发表时间：
2003-04-01
期刊：
影响因子：
3.4
通讯作者：
Boomsma, JJ
中科院分区：
文献类型：
--
作者：
Currie, CR;Bot, ANM;Boomsma, JJ
共生体塑造了生物组织的各个层次。虽然共生体的相互作用通常被视为二分协会，两个生物体相互作用主要是在隔离其他生物体，其他共生体的存在和重要性变得越来越明显。本研究探讨了切叶蚁及其真菌品种之间的古老共生关系中的第三个互利互惠的重要性。具体而言，我们实验研究的作用，丝状细菌（放线菌），这是通常进行的真菌生长的蚂蚁的角质层，在抑制生长的一个专门的微真菌寄生虫（Escovopsis）的真菌花园。我们进行了二乘二析因设计实验交叉放线菌的存在/不存在与存在/不存在的Escovopsis小亚克隆Acromyrmex spinosus内。在这些实验中，Escovopsis的感染在真菌花园中变得更加广泛，并且与细菌仍然存在于蚂蚁身上的花园相比，在从工人身上移除细菌的那些亚群中对gat-dens的健康产生更大的影响。我们建立了放线菌细菌是最丰富的主要工人照顾花园，提供进一步的支持，细菌参与花园卫生。我们还发现，与未感染的对照菌落相比，在实验感染Escovopsis的菌落中，工人身上的放线菌丰度显著更高。我们认为，共生生产微生物和高等生物之间的互惠可能是常见的协会，大多被忽视，共生体在减少寄生虫的影响的作用可能是互惠的成本效益评估的一个重要方面。
Symbioses shape all levels of biological organization. Although symbiotic interactions are typically viewed as bipartite associations, with two organisms interacting largely in isolation from other organisms, the presence and importance of additional symbionts is becoming increasingly more apparent. This study examines the importance of a third mutualist within the ancient symbiosis between leaf-cutting ants and their fungal cultivars. Specifically, we experimentally examine the role of a filamentous bacterium (actinomycete), which is typically carried on the cuticle of fungus-growing ants, in suppressing the growth of a specialized microfungal parasite (Escovopsis) of the fungus garden. We conducted two-by-two factorial design experiments crossing the presence/absence of actinomycete with the presence/absence of Escovopsis within small sub-colonies of Acromyrmex octospinosus. In these experiments, infection by Escovopsis became much more extensive within fungus gardens and had a greater impact on the health of gat-dens in those sub-colonies with the bacterium removed from workers as compared to gardens with the bacterium still present on the ants. We establish that the actinomycete bacterium is most abundant on those major workers tending the garden, providing further support that the bacterium is involved in garden hygiene. We also found a significantly higher abundance of actinomycete on workers in colonies experimentally infected with Escovopsis as compared to uninfected control colonies. We suggest that mutualisms between antibiotic-producing microbes and higher organisms may be common associations that are mostly overlooked and that the role of symbionts in reducing the impact of parasites is likely an important aspect in the cost-benefit assessment of mutualisms.