Aug. 28, 2012
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It was discovered that the 12_8 release has an issue with the OTUs. 
Specifically, the OTUs tar.gz with the MD5 of:

685182816c1e91be571d8328c7ac1865

are based off of the ssu-mask'd sequences, not the full reads. The result is 
that the OTU structure is likely not actually 99%. This issue could affect 
the topology and taxonomy of Greengenes. However, a comparison between the 
12_8 release and the previous release showed the taxonomy to be highly 
consistant so, while this release is flawed, it is not necessarily wrong. 

The necessary steps are being recomputed right now and an updated release will
be posted, likely as 12_8_1. 

I apologize for any inconvience

Daniel McDonald
mcdonadt@colorado.edu