Currie C R
Department of Ecology and Evolutionary Biology, 2041 Haworth Hall, University of Kansas, Lawrence, Kansas 66045-7534, USA.
Annu Rev Microbiol. 2001;55:357-80. doi: 10.1146/annurev.micro.55.1.357.
The ancient and highly evolved mutualism between fungus-growing ants and their fungi is a textbook example of symbiosis. The ants carefully tend the fungus, which serves as their main food source, and traditionally are believed to be so successful at fungal cultivation that they are able to maintain the fungus free of microbial pathogens. This assumption is surprising in light of theories on the evolution of parasitism, especially for those species of ants that have been clonally propagating their cultivars for millions of years. Recent work has established that, as theoretically predicted, the gardens of fungus-growing ants are host to a specialized, virulent, and highly evolved fungal pathogen in the genus Escovopsis. In addition, the ants have evolved a mutualistic association with filamentous bacteria (actinomycetes) that produce antibiotics that suppress the growth of Escovopsis. Thus, the attine symbiosis appears to be a coevolutionary "arms race" between the garden parasite Escovopsis on the one hand and the ant-fungus-actinomycete tripartite mutualism on the other. These recent findings indicate that microbes may be key components in the regulation of other symbiotic associations between higher organisms.
培育真菌的蚂蚁与其真菌之间古老且高度进化的共生关系是共生现象的典型教科书案例。蚂蚁精心照料作为其主要食物来源的真菌，传统观点认为它们在真菌培育方面非常成功，能够使真菌免受微生物病原体的侵害。鉴于寄生现象进化的理论，这一假设令人惊讶，尤其是对于那些已经克隆繁殖其培育品种数百万年的蚂蚁物种而言。最近的研究已经证实，正如理论预测的那样，培育真菌的蚂蚁的菌圃中存在一种属于埃斯科沃普氏菌属的特殊、致命且高度进化的真菌病原体。此外，蚂蚁已经与丝状细菌（放线菌）进化出一种共生关系，这些细菌会产生抑制埃斯科沃普氏菌生长的抗生素。因此，切叶蚁共生关系似乎是一场协同进化的“军备竞赛”，一方是菌圃寄生虫埃斯科沃普氏菌，另一方是蚂蚁 - 真菌 - 放线菌三方共生关系。这些最新发现表明，微生物可能是高等生物之间其他共生关系调节中的关键组成部分。
