Note: Exiguobacterium sibiricum 255-15 has replaced Exiguobacterium strain 255-15, 4/7/08.

Exiguobacterium sibiricum 255-15 was isolated from a 2-3 million-year permafrost core (Vishnivetskaya, T. et al. 2000). The permafrost samples were obtained from the Kolyma-Indigirka lowland, Siberia by David Gilichinsky (Russian Academy of Sciences, Pushchino, Russia).

The nearest phylogenetic neighbors to isolate 255-15
were other Kolyma-Indigirka lowland permafrost isolates
and grouped closely with the type strain (ATCC 953), isolated from skimmed milk and an Antarctic isolate of
Exiguobacterium acetylicum (Collins, M. D. et al. 1983),
(Farrow, J. A. E. et al. 1994).

Exiguobacterium sibiricum 255-15 is a non-spore forming Gram positive bacterium. The cells are short rods about 1 µm in length, with rounded ends. They occur singly, in pairs or infrequently in chains. Colonies appear orange-yellow on TSA media and the pigment does not diffuse into the medium. They are facultative anaerobes but grow more profusely aerobically.

This strain was chosen for sequencing based on its excellent survival after exposure to a long-term freeze, rapid growth at low temperatures, osmotic tolerance and age of the permafrost sediment from which it was cultured.

Through analysis of the transcriptome, experiments can be designed to study microbial survival under a variety of harsh conditions. The issue of long-term survival is of interest in the field of astrobiology. Organisms that survive such hostile environments may be used as models for understanding cellular responses on astral bodies.

References

1. Collins, M. D., B. M. Lund, J. A. E. Farrow and K. H. Schleifer (1983). 'Chemotaxanomic study of an alkalophilic bacterium, Exiguobacterium aurantiacum gen. Nov., sp. Nov.' Journal of General Microbiology 129: 2037-2042.

2. Farrow, J. A. E., S. Wallbanks and M. D. Collins (1994). 'Phylogenetic interrelationships of round-spore-forming Bacilli containing cell walls based on lysine and the non-spore-forming genera Caryophanon, Exiguobacterium, Kurthia, and Planococcus.' International Journal of Systematic Bacteriology 44: 74-82.

3. Vishnivetskaya, T., S. Kathariou, J. McGrath and J. M. Tiedje (2000). 'Low temperature recovery strategies for the isolation of bacteria from ancient permafrost sediments.' Extremophiles 4.165-173.