Figure 4.

Phylogenetic distribution of bacterial 16S rRNA cDNA (a) and mcrA and mrtA (b) sequences of [¹³C]- and [¹²C]-glucose treatments. Sequences were assigned to bacterial phyla with the RDP Classifier. Assignment of sequences to methanogenic families was based on ⩽75.4% gene sequence similarities (Hunger et al., 2011). As indicated in the lower axes, sequence analyses were performed for the total number of sequences (lane designated all), for all sequences at the start (t₀) or at 24 h (t₂₄) of incubation and for each fraction per time point and treatment. H, ‘heavy' fractions; L, ‘light' fraction; t₀, sampling point at the start of incubation; t₂₄, sampling point at 24 h of incubation; 13 and 12, [¹³C]- and [¹²C]-glucose treatments, respectively.