Estimation of gut metagenome size

In order to compare the different SRA samples for their β-glucuronidase sequence abundance, it is necessary to normalize our results to the metagenome size. To estimate the metagenome size we used MetaPhyler version 1.25 [32,33]. MetaPhyler is a taxonomic classifier for metagenomic shotgun reads that uses a set of universal, single-copy phylogenetic marker genes as a taxonomic reference [34]. We used the “blastn” option, which is recommended for short reads. We provide an example code for using MetaPhyler on GitHub [22].