medoids is a data.frame object containing the medoide sequences for each genus in
the ConTax data sets (both contax.trim and contax.full).
The medoide sequence in a genus is the sequence having the smallest sum of distance to all other members
of the same genus. Thus, it is the sequence closest to the centre of the genus. The medoids can be used as
the representative of each genus, e.g. for building trees for the entire taxonomy.
The taxonomy information for each sequence can be extracted from the Header column by the supplied
extractor-functions getDomain, getPhylum,...,getGenus.