boxB and 16S rRNA gene in silico amplicons identified in representative metagenomes using De-MetaST-BLAST.

aThe primers boxB171F (5′ CARGGNGAYACNGARCC 3′) and boxB265R (5′ YTTNCCRTCNCKRTCNGT 3′) were used to target an approximately 300 bp region of boxB.bUnique reads were identified using MOTHUR (v.1.27.0) [46].cThe primers 358f (5′CCTACGGGAGGCAGCAG3′) and 517r (5′ATTACCGCGGCTGCTGG3′) [47] were used to target an approximately 190 bp amplicon in the 16S rRNA gene.dAverage read length was estimated by dividing the database size by number of reads. The AntarcticaAquatic database is dominated by pyrosequencing derived reads (98% of all reads), while the GOS dataset is dominated by Sanger derived reads; the exact distribution for GOS reads is not available.