Jani Andrea J, Knapp Roland A, Briggs Cheryl J
Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, CA 93546, USA.
Proc Biol Sci. 2017 Jun 28;284(1857). doi: 10.1098/rspb.2017.0944.
Infectious diseases have serious impacts on human and wildlife populations, but the effects of a disease can vary, even among individuals or populations of the same host species. Identifying the reasons for this variation is key to understanding disease dynamics and mitigating infectious disease impacts, but disentangling cause and correlation during natural outbreaks is extremely challenging. This study aims to understand associations between symbiotic bacterial communities and an infectious disease, and examines multiple host populations before or after pathogen invasion to infer likely causal links. The results show that symbiotic bacteria are linked to fundamentally different outcomes of pathogen infection: host-pathogen coexistence (endemic infection) or host population extirpation (epidemic infection). Diversity and composition of skin-associated bacteria differed between populations of the frog, , that coexist with or were extirpated by the fungal pathogen, (Bd). Data from multiple populations sampled before or after pathogen invasion were used to infer cause and effect in the relationship between the fungal pathogen and symbiotic bacteria. Among host populations, variation in the composition of the skin microbiome was most strongly predicted by pathogen infection severity, even in analyses where the outcome of infection did not vary. This result suggests that pathogen infection shapes variation in the skin microbiome across host populations that coexist with or are driven to extirpation by the pathogen. By contrast, microbiome richness was largely unaffected by pathogen infection intensity, but was strongly predicted by geographical region of the host population, indicating the importance of environmental or host genetic factors in shaping microbiome richness. Thus, while both richness and composition of the microbiome differed between endemic and epidemic host populations, the underlying causes are most likely different: pathogen infection appears to shape microbiome composition, while microbiome richness was less sensitive to pathogen-induced disturbance. Because higher richness was correlated with host persistence in the presence of Bd, and richness appeared relatively stable to Bd infection, microbiome richness may contribute to disease resistance, although the latter remains to be directly tested.
传染病对人类和野生动物种群有着严重影响，但疾病的影响可能各不相同，即使在同一宿主物种的个体或种群之间也是如此。确定这种变异的原因是理解疾病动态和减轻传染病影响的关键，但在自然爆发期间厘清因果关系极具挑战性。本研究旨在了解共生细菌群落与一种传染病之间的关联，并在病原体入侵之前或之后检查多个宿主种群，以推断可能的因果联系。结果表明，共生细菌与病原体感染的根本不同结果相关联：宿主 - 病原体共存（地方病感染）或宿主种群灭绝（流行病感染）。与真菌病原体 （蛙壶菌，Bd）共存或被其灭绝的青蛙种群之间，皮肤相关细菌的多样性和组成存在差异。利用病原体入侵之前或之后对多个种群进行采样的数据，推断真菌病原体与共生细菌之间关系的因果。在宿主种群中，即使在感染结果没有变化的分析中，皮肤微生物组组成的变异也最强烈地由病原体感染严重程度预测。这一结果表明，病原体感染塑造了与病原体共存或被病原体驱使灭绝的宿主种群之间皮肤微生物组的变异。相比之下，微生物组丰富度在很大程度上不受病原体感染强度的影响，但强烈地由宿主种群的地理区域预测，这表明环境或宿主遗传因素在塑造微生物组丰富度方面的重要性。因此，虽然地方病和流行病宿主种群之间微生物组的丰富度和组成都有所不同，但其潜在原因很可能不同：病原体感染似乎塑造了微生物组组成，而微生物组丰富度对病原体引起的干扰不太敏感。因为较高的丰富度与在存在蛙壶菌的情况下宿主的持久性相关，并且丰富度对蛙壶菌感染似乎相对稳定，所以微生物组丰富度可能有助于抗病性，尽管后者仍有待直接测试。
