Isolation of a 250 million-year-old halotolerant bacterium from a primary salt crystal

Abstract

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).

Absence of Yersinia pestis-specific DNA in human teeth from five European excavations of putative plague victims

“…Christner et al (2000) reported unsuccessful attempts at replicating aDNA detection from bacteria within Greenland ice cores (Catranis & Starmer, 1991;Ma et al, 1999). Graur & Pupko (2001) and Nickle et al (2002) have been unable to replicate detection of the 250 million-year-old halotolerant bacterium of Vreeland et al (2000).…”

The Bacillus subtilis spore coat provides “eat resistance” during phagocytic predation by the protozoan Tetrahymena thermophila

“…The spores are metabolically dormant and very resistant to a variety of environmental stress factors including heat, radiation, desiccation, and freeze-thaw cycles (1). As a consequence of their dormancy and resistance, spores can survive for very long periods, certainly hundreds of years, and there are reports suggesting that spores may even survive for millions of years (2)(3)(4).…”

Searching for life: the case for Halobacteria on Mars

“…Dried inside salt crystals, the_ blow thousands of miles in the form_vindblown dust and salt, and by this means colonize transient small pools_'high concentration brine (Armstrong, 1981;Armstrong, 1982;Vreeland, Rosenzweig, and Powers, 2000). Another species which could be a terrestrial analogue for Martian life is the "desert varnish" (Dorn, and Oberlander, 1981), which can utilize transient occurrences of extremely small amounts of water to maintain metabolism in a normally-dry environment.…”