Fig. 3

Abundance of Methylocella in relation to total bacteria (a) and pmoA-containing methanotrophs (b). Bacterial populations were enumerated by qPCR of 16S rRNA (for total bacteria), Methylocella-specific mmoX (for Methylocella) and pmoA (for pmoA-containing methanotrophs) genes on environmental DNA samples. Methylocella cell numbers equate to Methylocella-specific mmoX gene copies, whereas bacteria and pmoA-containing methanotrophs were assumed to contain two 16S rRNA or pmoA gene copies per cell. Bacteria other than Methylocella were enumerated by subtracting Methylocella from total bacterial cell numbers. Error bars represent the propagated errors based on standard deviation of triplicate samples