Description:A constituent taxon of either (a) a subject assigned to the 'environmental microbiome' granularity category or (b) the microbiome (non-host) portion of a subject assigned to the 'host-associated microbiome' granularity category [NB: This role is probably not appropriate for Level 1, because it necessitates the post-facto attachment of downstream analysis procedures (subject -> sample -> library prep -> sequencing -> bioinformatics -> taxonomic classification results) to a subject which was originally uncharacterized at this level]