FIG 3.

Comparison of primer performance versus depth using the three general mcrA primer pairs. (Top panel) mcrIRD primer pair; (middle panel) mcrI primer pair; (bottom panel) ME1/ME2 primer pair. After these initial clone libraries, which led to the use of the mcrIRD primer pair from then on, additional sequencing on new PCR products was done with the mcrIRD primer pair, resulting in detection of further clusters (Table 3). We omit these results here to make primer performances more comparable.