Robak Matthew J, Richards-Zawacki Corinne L
Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, LA, United States.
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, United States.
Front Microbiol. 2018 Mar 7;9:410. doi: 10.3389/fmicb.2018.00410. eCollection 2018.
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 affect the susceptibility of amphibian hosts to infection by , 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 (), prior to exposing these animals to 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, , 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 infection), and frogs with skin bacterial communities augmented with the known antifungal bacterium would be less susceptible to 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 -exposed frogs. Whether temperature affected survival; however, it differed among our skin microbial treatment groups, with animals having more on their skin surviving longer at 14 but not at 26°C. Our results suggest that temperature was the predominant factor influencing '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 infection.
抵御病原体是细菌为动物宿主带来的众多益处之一。为了预测新出现的动物疾病的影响和动态，需要更清楚地了解环境变化如何影响动物与其微生物有益菌之间的相互作用。由于温度对动物及其病原体的生理有显著影响，它可能是调节有益细菌为其动物宿主提供保护水平的关键变量。在这里，我们研究温度和皮肤微生物群落的组成如何影响两栖动物宿主对两种已知会导致壶菌病的真菌病原体之一——的感染易感性。为此，我们在将易感宿主北方豹蛙暴露于两种不同的与生态相关的温度下之前，对其皮肤细菌群落进行了操控。我们的操控包括一种使用抗生素来减少皮肤细菌群落的处理，一种用抗真菌细菌增强细菌群落的处理，以及一种让青蛙皮肤细菌群落保持完整的处理。我们预测皮肤细菌群落减少的青蛙会更易感染（即对感染的抵抗力和/或耐受性更低），而皮肤细菌群落用已知抗真菌细菌增强的青蛙对感染和壶菌病的易感性会更低。然而，我们也预测这种相互作用会依赖于温度。我们发现温度对暴露于的青蛙的感染概率和强度有强烈影响，但皮肤微生物处理没有影响。温度是否影响存活率；然而，在我们的皮肤微生物处理组中有所不同，皮肤携带更多的动物在14°C时存活时间更长，但在26°C时并非如此。我们的结果表明，温度是影响定殖于宿主能力（即抵抗力）的主要因素，但皮肤细菌群落的组成在调节宿主在重度感染下存活的能力（即耐受性）方面很重要。
