In response to Burt Guttman:
Yes, much of the DNA will be from bacteria and phage. However, if you
choose an appropriate DNA primer, that is specific to the vertebrate in
question, and ampflify the sequence with PCR, you can isolate the
vertebrate DNA. There is already a claim in the literature for this
being accomplished in chimps in Africa-the researchers plan on using it
do determine family trees without having to draw blood samples. They
just need to observe which animal leaves the dropping and then use a
primer specific for a DNA sequence specfic to chimp which is not in the
bacteria. So it is possible-current PCR tecnahiques could work if only 1
epithileal cell is present.

Jim Neitzel
neitzelj at elwha.evergreen.edu