FIG 1.

Normalized abundances of multiheme c-type cytochromes (MHCs) (a), MHCs with putative EET functions (i.e., MHCs in PCC and outer surface MHCs not associated with PCC) (b), and Cyc2 homologs (c) found in metagenomes obtained from Lake Mendota’s epilimnion (ME), and Trout Bog’s epilimnion (TE) and hypolimnion (TH), respectively. (a and b) Normalized abundance was reported for MHCs with 5 to 10 and >10 heme binding sites, respectively. The normalized abundance was obtained by mapping metagenome reads to assembled contigs, and the read coverage was then normalized by the average read coverage of single-copy conserved bacterial housekeeping genes in the same metagenome. See Text S1 in the supplemental material for details on the calculation of normalized abundance.