Data from: Temperature dependent effects of cutaneous bacteria on a frog's tolerance of fungal infection

Defense against pathogens is one of many benefits that bacteria provide to animal hosts. A clearer understanding of how changes in the environment affect the interactions between animals and their microbial benefactors is needed in order to predict the impact and dynamics of emerging animal diseases. Due to its dramatic effects on the physiology of animals and their pathogens, temperature may be a key variable modulating the level of protection that beneficial bacteria provide to their animal hosts. Here we investigate how temperature and the makeup of the skin microbial community impact the susceptibility of amphibian hosts to infection by Batrachochytrium dendrobatidis, one of two fungal pathogens known to cause the disease chytridiomycosis. To do this, we manipulated the skin bacterial communities of susceptible hosts, northern cricket frogs (Acris crepitans), prior to exposing these animals to Batrachochytrium dendrobatidis under two different ecologically relevant temperatures. Our manipulations included one treatment where antibiotics were used to reduce the skin bacterial community, one where the bacterial community was augmented with the antifungal bacterium, Stenotrophomonas maltophilia, and one in which the frog's skin bacterial community was left intact. We predicted that frogs with reduced skin bacterial communities would be more susceptible (i.e., less resistant to and/or tolerant of Bd infection), and frogs with skin bacterial communities augmented with the known antifungal bacterium would be less susceptible to Bd infection and chytridiomycosis. However, we also predicted that this interaction would be temperature-dependent. We found a strong effect of temperature but not of skin microbial treatment on the probability and intensity of infection in Bd-exposed frogs. Whether temperature impacted survival, however, differed among our skin microbial treatment groups, with animals having more S. maltophilia on their skin surviving longer at 14 but not at 26 °C. Our results suggest that temperature was the predominant factor influencing Bd's ability to colonize the host (i.e., resistance) but that the composition of the cutaneous bacterial community was important in modulating the host's ability to survive (i.e., tolerate) a heavy Bd infection.病原菌防御是细菌为动物宿主提供的诸多益处之一。为了预测新兴动物疾病的影响与动态变化，我们需要更清晰地理解环境变化如何影响动物与其微生物益生菌之间的互作关系。温度对动物及其病原菌的生理机能具有显著影响，因此可能是调控有益细菌为宿主提供保护水平的关键变量。本研究探讨了温度与皮肤微生物群落组成如何影响两栖动物宿主感染蛙壶菌（Batrachochytrium dendrobatidis）的易感性——该菌是已知引发壶菌病（chytridiomycosis）的两种真菌病原菌之一。为此，我们在易感宿主——北方蟋蟀蛙（Acris crepitans）——暴露于两种不同生态相关温度下的蛙壶菌之前，对其皮肤细菌群落进行了操控处理。我们的操控处理包含三组：一组使用抗生素削弱皮肤细菌群落，一组通过添加抗真菌细菌嗜麦芽窄食单胞菌（Stenotrophomonas maltophilia）来丰富细菌群落，还有一组保留青蛙的皮肤细菌群落完整无干预。我们推测，皮肤细菌群落被削弱的青蛙会更易感染（即对Bd感染的抗性和/或耐受性更低），而皮肤细菌群落经已知抗真菌细菌富集的青蛙则对Bd感染及壶菌病的易感性更低。但我们同时预测，这种互作关系会受到温度的调控。我们发现，在暴露于Bd的青蛙中，温度对感染概率与感染强度存在显著影响，但皮肤微生物处理组无此效应。不过，温度对存活率的影响因皮肤微生物处理组而异：当环境温度为14℃时，皮肤携带更多S. maltophilia的个体存活时间更长，但在26℃时未观察到此现象。我们的研究结果表明，温度是影响Bd定植宿主能力（即宿主抗性）的主要因素，而皮肤细菌群落的组成则在调控宿主应对重度Bd感染的存活能力（即宿主耐受性）方面发挥关键作用。