Sample collection and DNA extraction
Genomic DNA from microbial mock community B (even, low concentration), v5.1 L, catalog no. HM-782D for 16 S rRNA microbiota profiling was obtained from BEI Resources, NIAID, NIH as part of the Human Microbiome Project and consists of genomic DNA from 20 bacterial strains with equimolar ribosomal RNA operon counts (100,000 copies per organism per μL). The microbial mock community contains species with different rRNA copy numbers in their genomes, ranging from two for Helicobacter pylori to 14 for Clostridium beijerinckii. Nose swabs and fecal samples were collected from healthy adult volunteers. DNA was extracted from both types of samples using the QIAsymphony instrument (Qiagen) according to the manufacturer’s instructions. DNA was extracted from three sludge samples from river bed, using the Powersoil DNA isolation kit (MO BIO Laboratories, Inc.). The total number of 16 S rRNA genes within each sample was quantified as described previously18. Prior to use as template for micelle and traditional PCR amplification the samples were normalized to 1E + 03 16 S rRNA genes/μL (nasal swabs) or 1E+05 16S rRNA genes/μL (feces and sludge samples).