Fig 2.

Relative abundances of T-RFs, after digestion with MspI, which represent key nitrifying and heterotrophic populations in the light and heavy fractions of the density gradients after RNA-SIP. The analysis was conducted after the samples had been incubated for 21 days. Error bars show 1 standard deviation (two replicates). Missing data points indicate that no PCR amplicon could be obtained at these gradient densities in the respective experiment. Circles represent the experiment with NH₄⁺ as the energy source and H¹³CO₂⁻ as the carbon source, squares the control experiment with NH₄⁺ and H¹²CO₂⁻, and triangles the control experiment without any added energy source and H¹³CO₂⁻ (in this control experiment, Thermomonas T-RF 190 was not detected above the threshold applied for peak calling). Note the different y axis scales in the graphs.