Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
Department of Biology, University of Pennsylvania, Philadelphia, PA, USA.
Proc Biol Sci. 2021 Aug 11;288(1956):20211313. doi: 10.1098/rspb.2021.1313.
Interactions among parasites and other microbes within hosts can impact disease progression, yet study of such interactions has been mostly limited to pairwise combinations of microbes. Given the diversity of microbes within hosts, indirect interactions among more than two microbial species may also impact disease. To test this hypothesis, we performed inoculation experiments that investigated interactions among two fungal parasites, and and a systemic fungal endophyte, within the grass, tall fescue (). Both direct and indirect interactions impacted disease progression. While the endophyte did not directly influence disease progression or symptom development, the endophyte modified the interaction between the two parasites The magnitude of the facilitative effect of on the growth of tended to be greater when the endophyte was present. Moreover, this interaction modification strongly affected leaf mortality. For plants lacking the endophyte, parasite co-inoculation did not increase leaf mortality compared to single-parasite inoculations. By contrast, for endophyte-infected plants, parasite co-inoculation increased leaf mortality compared to inoculation with or alone by 1.9 or 4.9 times, respectively. Together, these results show that disease progression can be strongly impacted by indirect interactions among microbial symbionts.
宿主内寄生虫和其他微生物之间的相互作用会影响疾病的进展，但此类相互作用的研究大多仅限于对两种微生物的两两组合。鉴于宿主内微生物的多样性，两种以上微生物物种之间的间接相互作用也可能影响疾病。为了验证这一假设，我们进行了接种实验，研究了真菌寄生虫 和 以及系统真菌内生菌 在草类高羊茅中的相互作用。直接和间接相互作用都影响了疾病的进展。内生菌虽然不会直接影响 疾病的进展或 症状的发展，但它改变了两种寄生虫之间的相互作用。内生菌存在时， 对 的生长的促进作用幅度往往更大。此外，这种相互作用的改变强烈影响了叶片死亡率。对于缺乏内生菌的植物，与单一寄生虫接种相比，寄生虫共同接种不会增加叶片死亡率。相比之下，对于内生菌感染的植物，寄生虫共同接种与单独接种 或 相比，叶片死亡率分别增加了 1.9 倍和 4.9 倍。综上所述，这些结果表明，疾病的进展可能会受到微生物共生体之间的间接相互作用的强烈影响。
