Temperature variation underlies turnover of bacterial diversity and fungal infection dynamics in the amphibian skin. skin metagenome

Host-associated bacterial communities on the skin act as the first line of defense against invading pathogens. Yet, for most natural systems, we lack a clear understanding of how seasonal variability affects structure and composition of skin bacterial communities, and in turn, promotes or limits the colonization of opportunistic pathogens. Here, we ask whether the loss of putatively beneficial bacteria predisposes hosts to subsequent infections. We report on a spatiotemporal study of three amphibian populations infected by the pathogenic fungus Batrachochytrium dendrobatidis (Bd). Our focal host species is a direct-developing frog (Eleutherodactylus coqui) that has suffered declines at some populations in the last 20 years, while others have not experienced any changes. We quantified skin bacterial alpha and beta diversity at four sampling time points, a period encompassing two seasons and ample variation in natural infections and environmental conditions. Despite the different patterns of infection across populations, we detected an overall increase in bacterial diversity through time, characterized by the replacement of bacterial species. Increased frog body temperatures over time allowed the colonization of bacteria and recruitment of putatively beneficial bacteria. Our results underscore how natural fluctuations in temperature and precipitation can create opportunities for bacterial replacement, potentially attenuating pathogen transmission, and thus contributing to host persistence in E. coqui populations.

栖息于宿主皮肤的细菌群落，是抵御入侵病原体的第一道防线。然而，针对绝大多数自然生态系统，我们仍尚未明确季节波动如何影响皮肤细菌群落的结构与组成，进而如何调控机会性致病菌的定殖过程。本研究旨在探讨：推定有益菌的丧失是否会使宿主更易继发感染。本研究针对3个感染致病性真菌蛙壶菌（Batrachochytrium dendrobatidis, Bd）的两栖动物种群开展了时空动态调查。本研究的目标宿主为直接发育型蛙类——科奎蛙（Eleutherodactylus coqui）：在过去20年间，部分该物种的种群数量出现下降，而其余种群则未发生明显变化。我们在4个采样时间点对其皮肤细菌的α多样性与β多样性进行了定量分析，采样周期覆盖两个季节，涵盖了自然感染与环境条件的显著波动。尽管不同种群的感染模式存在差异，但我们整体观测到细菌多样性随时间推移呈上升趋势，其核心特征为细菌物种的更替。蛙类体温随时间升高，推动了细菌的定殖与推定有益菌的招募。本研究结果凸显了温度与降水的自然波动如何为细菌物种更替创造条件，进而可能减弱病原体的传播能力，最终助力科奎蛙种群的宿主存续。