(Required). A character string that is the full URL path to a zipped file that follows the file naming conventions used by microbio.me/qiime. Alternatively, you can simply provide the study number as a single integer or other single-length vector that can be coerced to an integer; this function will complete the remainder of the ftp URL hosted at microbio.me/qiime. For example, instead of the full URL string, "ftp://thebeast.colorado.edu/pub/QIIME_DB_Public_Studies/study_494_split_library_seqs_and_mapping.zip", you could simply provide 494 or "494" as the first ('zipftp') argument.

(Optional). A character string of the expected file extension, which also indicates the compression type, if zipftp is a study number instead of the full path. Note that this argument has no effect if zipftp is the full path, in which case the file extension is read directly from the downloaded file.

(Optional). The type of taxonomic parsing to use for the OTU taxonomic classification, in the .biom file, if present. This is passed on to import_biom, but unlike that function the default parsing function is parse_taxonomy_greengenes, rather than parse_taxonomy_default, because we know ahead of time that most (or all?) of the taxonomic classifications in the microbio.me/qiime repository will be based on GreenGenes.

(Optional, for advanced users). Additional arguments passed to download.file. This is mainly for non-standard links to resources (in this case, a zipped file) that are not being hosted by microbio.me/qiime. If you are using a FTP address or study number from their servers, then you shouldn't need to provide any additional arguments.