Physiological responses of soil microorganisms to global warming are important for soil ecosystem function and the terrestrial carbon cycle. Here, we investigate the effects of weeks, years, and decades of soil warming across seasons and time on the microbial protein biosynthesis machineries (i.e. ribosomes), the most abundant cellular macromolecular complexes, using RNA:DNA and RNA:MBC (microbial biomass carbon) ratios as proxies for cellular ribosome contents. We compared warmed soils and non-warmed controls of 15 replicated subarctic grassland and forest soil temperature gradients subject to natural geothermal warming. RNA:DNA ratios tended to be lower in the warmed soils during summer and autumn, independent of warming duration (6 weeks, 8–14 years, > 50 years), warming intensity (+3°C, +6°C, +9°C), and ecosystem type. With increasing temperatures RNA:MBC ratios were also decreasing. Additionally, seasonal RNA:DNA ratios of the consecutively sampled forest showed the same temperature-driven pattern. This suggests that subarctic soil microorganisms are depleted of ribosomes under warm conditions and the lack of consistent relationships with other physicochemical parameters besides temperature further suggests temperature as key driver. Furthermore, in incubation experiments, we measured significantly higher CO2 emission rates per unit of RNA from short- and long-term warmed soils compared to non-warmed controls. In conclusion, ribosome reduction may represent a widespread microbial physiological response to warming that offers a selective advantage at higher temperatures, as energy and matter can be reallocated from ribosome synthesis to other processes including substrate uptake and turnover. This way, ribosome reduction could have a substantial effect on soil carbon dynamics.

中文翻译：

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在短期、中期和长期变暖的情况下，亚北极土壤中的微生物核糖体被耗尽

土壤微生物对全球变暖的生理反应对于土壤生态系统功能和陆地碳循环具有重要意义。在这里，我们使用 RNA:DNA 和 RNA:MBC（微生物生物质碳）比率作为细胞核糖体含量的代表。我们比较了受自然地热变暖影响的 15 个复制的亚北极草原和森林土壤温度梯度的变暖土壤和非变暖对照。夏季和秋季变暖的土壤中 RNA:DNA 比率往往较低，与变暖持续时间（6 周、8-14 年、> 50 年）、变暖强度（+3°C、+6°C、+ 9°C）和生态系统类型。随着温度升高，RNA:MBC 比率也在下降。此外，连续采样的森林的季节性 RNA:DNA 比率显示出相同的温度驱动模式。这表明亚北极土壤微生物在温暖条件下耗尽核糖体，并且与温度以外的其他物理化学参数缺乏一致的关系，进一步表明温度是关键驱动因素。此外，在孵化实验中，我们测量到与未变暖的对照相比，短期和长期变暖的土壤中每单位 RNA 的二氧化碳排放率显着更高。总之，核糖体减少可能代表了微生物对变暖的广泛生理反应，在较高温度下提供了选择性优势，因为能量和物质可以从核糖体合成重新分配到包括底物吸收和周转在内的其他过程。这样，核糖体的减少可能对土壤碳动态产生重大影响。