Isolation of a 250 million-year-old halotolerant bacterium

Rcjohnsen rcjohnsen at
Sat Oct 21 17:24:26 EST 2000

19 October 2000 
Nature 407, 897 - 900 (2000) © Macmillan Publishers Ltd. 
Isolation of a 250 million-year-old halotolerant bacterium from a primary salt
Bacteria have been found associated with a variety of ancient samples, however
few studies are generally accepted due to questions about sample quality and
contamination. When Cano and Borucki isolated a strain of Bacillus sphaericus
from an extinct bee trapped in 25–30 million-year-old amber, careful sample
selection and stringent sterilization techniques were the keys to acceptance.
Here we report the isolation and growth of a previously unrecognized
spore-forming bacterium (Bacillus species, designated 2-9-3) from a brine
inclusion within a 250 million-year-old salt crystal from the Permian Salado
Formation. Complete gene sequences of the 16S ribosomal DNA show that the
organism is part of the lineage of Bacillus marismortui and Virgibacillus
pantothenticus. Delicate crystal structures and sedimentary features indicate
the salt has not recrystallized since formation. Samples were rejected if brine
inclusions showed physical signs of possible contamination. Surfaces of salt
crystal samples were sterilized with strong alkali and acid before extracting
brines from inclusions. Sterilization procedures reduce the probability of
contamination to less than 1 in 10 9. 

Nature © Macmillan Publishers Ltd 2000 Registered No. 785998 England.   
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