The Waste Isolation Pilot Plant (WIPP) is a salt mine constructed 650
meters below the ground surface by the United States Department of Ene
rgy. The facility will be used for permanent disposal of transuranic w
astes. This underground repository has been constructed in the geologi
cally stable Permian age Salado salt formation. Of the wastes to be pl
aced into the facility, 85% will be biodegradable cellulose. A 3-year
survey of the bacterial populations existing within the facility was c
onducted. Bacterial populations were found to be heterogeneously distr
ibuted throughout the mine. Populations in some mine areas reached as
high as 1.0 x 10(4) colony-forming units per gram of NaCl. The heterog
eneous distribution of bacteria within the mine did not follow any rec
ognizable pattern related to either age of the workings or to human ac
tivity. A biochemical comparison between ten known species of halophil
ic bacteria, and strains isolated from both the mine and nearby surfac
e hypersaline lakes, showed the presence of extreme halophiles with wi
de biochemical diversity, some of which could prove to represent previ
ously undescribed groups. The halophilic bacteria isolated from the mi
ne were found to degrade cellulose and a wide variety of other carbon
compounds. When exposed to two types of common laboratory paper, the c
ellulose-degrading halophiles attached to the substrate within 30 minu
tes of inoculation. Cultures enriched directly from a brine seep in th
e mine easily destroyed both papers and produced detectable amounts of
oxalacetic and pyruvic acids. The combination of heterogeneity in the
distribution of organisms, the presence of a physiologically diverse
community, and the relatively slow metabolism of cellulose may explain
several long-standing debates about the existence of microorganisms i
n ancient underground salt formations.