September 29th, 2005
The keys to life in the extreme cold
A team from the Institut Pasteur and the CNRS, in collaboration with the Genoscope, has deciphered the clever mechanisms developed by a bacterium allowing it to flourish in the heart of Antarctica. In scrutinizing its genome, the researchers revealed several developments in this bacterium's metabolism that allow it both to resist very low temperatures and to flourish there quite effectively. Aside from the knowledge gained about the adaptability of life in extreme conditions, this research could make possible the development of new biotech tools based on this biological machinery that is adapted to extreme cold.
Starting a few years ago, many studies have been done on the adaptation of life to extreme conditions. But while the metabolism of organisms that develop in warm water sources is now beginning to be known, knowledge of bacteria capable of developing with great effectiveness below 15° C--a temperature found on nearly 3/4 of the planet--is new.
Researchers from the team of Antoine Danchin, director of the Institut Pasteur-CNRS Genetics of Bacterial Genomes Unit, used a bacterium, Pseudoalteromonas haloplanktis, that grows in the Antarctic, near the Dumont d’Urville research station. In collaboration with the Genoscope in Evry, the University of Hong Kong, and researchers from the Universities of Liège, Naples, and Stockholm, they scrutinized the genome of this bacterium and reconstructed the multiple metabolic tricks that allow it to flourish in an environment that is so hostile to humans. In this way, they found how the bacterium was able to adapt to the presence of atmospheric oxygen, which is very soluble in cold water and then becomes a highly toxic reactive element: instead of simply developing metabolic means to eliminate the toxic products resulting from this element, as other organisms do, P. haloplanktis, in contrast, optimises mechanisms which allow it to utilise the element directly as a source of energy. Furthermore, to keep its membrane fluid, and prevent it from freezing at low temperatures, it modifies its lipid composition with a particular enzyme that uses this same available oxygen and takes part in eliminating it, killing two birds with one stone.
In addition, many properties have been brought to light, like the concerted change in the amino acid composition of proteins. Organisms living at "normal" temperatures relatively infrequently use a delicate amino acid, asparagine, in spite of its advantageous properties, because it deteriorates chemically over time and is thus one of the most significant factors in aging. The P. haloplanktis bacterium, protected from aging by the cold, uses asparagine to a larger degree in its proteins.
The detailed analysis of all these new methods could open the way towards discovering tools that would, for example, allow the synthesis at low temperatures of advantageous or useful molecules, such as albumin, which are currently difficult to produce under standard conditions
« Coping with cold : The genome of the versatile marine Antarctica bacterium Pseudoalteromonas haloplanktis TAC125» Genome research , octobre 2005.
Claudine Médigue (1), Evelyne Krin (2), Géraldine Pascal (1,2), Valérie Barbe (1), Andreas Bernsel (3), Philippe N. Bertin (4), Frankie Cheung (5), Stéphane Cruveiller (1), Salvino D’Amico (6), Angela Duilio (7), Gang Fang (2), Georges Feller (6), Christine Ho (5), Sophie Mangenot (1), Gennaro Marino (7), Johan Nilsson (3), Ermenegilda Parrili (7), Eduardo P. C. Rocha (2), Zoé Rouy (1), Agnieszka Sekowska (2,8), Maria Luisa Tutino (7), David Vallenet (1), Gunnar von Heijne (3), et Antoine Danchin (2,9)
1. Genoscope, CNRS-UMR 8030 Atelier de Génomique Comparative, Evry, France
2. Unité de Génétique des Génomes Bactériens, Institut Pasteur, Paris, France
3. Department of Biochemistry and Biophysics, Université de Stockolhm, Suède
4. Dynamique, Evolution et Expression de Génomes de Micro-organismes, Université Louis Pasteur, Strasbourg, France
5. Computer Centre, The University of Hong Kong, Hong Kong
6. Laboratoire de Biochimie, Institut de Chimie B6, Université de Liège, Belgique
7. Dipartimento di Chimica Organica e Biochemica, Complesso Universitario Monte S. Angelo, Naples , Italie
8. Laboratoire Stress Oxydants et Cancer, CEA Saclay, Gif sur Yvette, France
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