GG97 is my name for the default closed-reference database used by QIIME. It is a subset of the Greengenes database (DeSantis et al. 2006) clustered at 97% identity.
The filename in QIIME is 97_otus.fasta. I am posting it here because to the
best of my knowledge it is not directly available for download; the only way
to get it is to install and run the
QIIME virtual box.