Department of Entomology, University of Georgia, Athens, GA 30602, USA.
Annu Rev Entomol. 2010;55:247-66. doi: 10.1146/annurev-ento-112408-085305.
Aphids engage in symbiotic associations with a diverse assemblage of heritable bacteria. In addition to their obligate nutrient-provisioning symbiont, Buchnera aphidicola, aphids may also carry one or more facultative symbionts. Unlike obligate symbionts, facultative symbionts are not generally required for survival or reproduction and can invade novel hosts, based on both phylogenetic analyses and transfection experiments. Facultative symbionts are mutualistic in the context of various ecological interactions. Experiments on pea aphids (Acyrthosiphon pisum) have demonstrated that facultative symbionts protect against entomopathogenic fungi and parasitoid wasps, ameliorate the detrimental effects of heat, and influence host plant suitability. The protective symbiont, Hamiltonella defensa, has a dynamic genome, exhibiting evidence of recombination, phage-mediated gene uptake, and horizontal gene transfer and containing virulence and toxin-encoding genes. Although transmitted maternally with high fidelity, facultative symbionts occasionally move horizontally within and between species, resulting in the instantaneous acquisition of ecologically important traits, such as parasitoid defense.
蚜虫与多样的可遗传细菌共生体进行共生。除了其必需的营养供应共生体布赫纳氏菌（Buchnera aphidicola）外，蚜虫还可能携带一种或多种兼性共生体。与必需共生体不同，兼性共生体通常不是生存或繁殖所必需的，并且可以根据系统发育分析和转染实验侵入新宿主。兼性共生体在各种生态相互作用中是互利共生的。豌豆蚜（Acyrthosiphon pisum）的实验表明，兼性共生体可以抵御昆虫病原真菌和寄生蜂，减轻热的不利影响，并影响宿主植物的适宜性。保护共生体汉密尔顿氏菌（Hamiltonella defensa）具有动态基因组，表现出重组、噬菌体介导的基因摄取以及水平基因转移的证据，并且含有毒力和毒素编码基因。尽管兼性共生体以高度保真度通过母体传递，但它们偶尔会在种内和种间进行水平传播，从而瞬时获得生态重要的特征，如寄生蜂防御。
