An. Rhodes et al., IDENTIFICATION OF BACTERIAL ISOLATES OBTAINED FROM INTESTINAL CONTENTS ASSOCIATED WITH 12,000-YEAR-OLD MASTODON REMAINS, Applied and environmental microbiology, 64(2), 1998, pp. 651-658
Mastodon (Mammut americanum) remains unearthed during excavation of an
cient sediments usually consist only of skeletal material, due to post
mortem decomposition of soft tissues by microorganisms. Two recent exc
avations of skeletal remains in anoxic sediments in Ohio and Michigan,
however, have uncovered organic masses which appear to be remnants of
the small and large intestines, respectively. Macrobotanical examinat
ions of the composition of these masses revealed assemblages of plant
material radiocarbon dated to approximately 11,500 years before the pr
esent and thought to be incompletely digested food remains from this e
xtinct mammal. We attempted to cultivate and identify bacteria from th
e intestinal contents, bone-associated sediments, and sediments not in
proximity to the remains using a variety of general and selective med
ia. In all, 295 isolates were cultivated, and 38 individual taxa were
identified by fatty acid-methyl ester (FAME) profiles and biochemical
characteristics (API-20E). The taxonomic positions of selected enteric
and obligately anaerobic bacteria were confirmed by 16S ribosomal DNA
(rDNA) sequencing. Results indicate that the intestinal and bone-asso
ciated samples contained the greatest diversity of bacterial taxa and
that members of the family Enterobacteriaceae represented 41% of all i
solates and were predominant in the intestinal masses and sediments in
proximity to the skeleton but were uncommon in the background sedimen
ts. Enterobacter cloacae was the most commonly identified isolate, and
partial rDNA sequencing revealed that Rahnella aquatilis was the corr
ect identity of strains suggested by FAME profiles to be Yersinia ente
rocolitica. No Bacteroides spp. or expected intestinal anaerobes were
recovered, The only obligate anaerobes recovered were clostridia, and
these were not recovered from the small intestinal masses. Microbiolog
ical evidence from this study supports other, macrobotanical data indi
cating the intestinal origin of these masses. Whether these organisms
are direct descendants of the original intestinal microbiota, however,
cannot be established.