RNA-DNA oscillatory dynamics reflect the physiological state of microbial communities

Microorganisms respond to environmental conditions via their physiology, but we lack an understanding of how this response translates to community dynamics. Here we evaluated the physiological response of microbes using a multi-year timeseries of paired ribosomal RNA and DNA from freshwater communities. The dynamics of RNA and DNA displayed strong seasonal oscillations, with phylogenetically distant species exhibiting similar timescales of response. Several universal macroecological patterns followed the predictions of the Stochastic Logistic Model of growth (e.g., gamma distributed abundances) while others displayed deviations due to the SLMs inability to account for oscillations (e.g., temporal autocorrelation). These deviations motivated the development of an oscillating SLM, with seasonal dynamics captured by the carrying capacity. Using this model, we found that DNA predicted future RNA:DNA ratios as a proxy of ribosome concentration, a result consistent with the view that RNA:DNA reflects growth. By examining environmental variables that displayed similar seasonality, we found that temperature provided a reasonable explanation of RNA:DNA dynamics. This work points towards a physiological framework for understanding seasonal dynamics in microbial communities.