ebme.marine.rutgers.edu papers/lee et …  · web viewgiven the widespread influence of lateral...

Dr. Kay D. BidleAssistant Professor x 393Fax: 732-932-4083bidle@marine.rutgers.edu

H. Jesse SmithSenior EditorScience 1200 New York Avenue NWWashington, DC 20005202-326-6556 18 July 2006

Dear Dr. Smith,

Enclosed please find a manuscript entitled “Fossil Genes and Microbes Entombed in the Oldest Ice on Earth” by Lee et al. for consideration for publication in Science. It reports our metabolic and genetic characterization of microbes and DNA encased in extremely slow-moving debris-covered glacier ice from the Dry Valleys region of the Transantarctic Mountains. The Antarctic continent offers unique environments for understanding the limits to geological and biological preservation of life and genetic material in immobilized dormant states. We have discovered that metabolic activity and cell viability have been retained in buried ice samples spanning an ~8 million year time transect and including the oldest known ice on Earth, although they were critically compromised with age. Our molecular analyses further revealed dramatic differences in DNA integrity between these ice samples, indicating that the average DNA size declines exponentially with time with a half-life of ~2.5 million years. These data provide unprecedented insight into the preservation of environmental DNA in ice.

Interestingly, our metagenomic analysis of preserved community DNA from these ancient ice samples found diverse orthologs to extant metabolic genes, making them literal “gene banks”, with deposits made when the ices formed 0.1 to ~ 8.1 My. Given the widespread influence of lateral gene transfer within microbial populations and its putative influence on the tempo of microbial evolution, one can envision pulsed periods of gene availability in environments that experience episodic periods of melting and freezing, like glaciers and pack ice, or snowball events. Hence, community DNA immobilized in Antarctic ice can be viewed as a “gene popsicle” that potentially can be acquired repaired, incorporated and used by viable microbes upon thawing. This means that such events may provide an opportunity for massive microbial gene transfers that alter metabolic potential, a prescient scenario given the current trends in climate change and global warming. Such events could have potentially “scrambled” microbial phylogenies several times in Earth’s history, and potentially accelerated the tempo of evolution.

Given that our results help to constrain the possible exchange of genetic material to the oceans, as well as the ability of viable microbes to traverse the solar system in comets as a potential mechanism of seeding habitable planets with life, we believe that our results will be of broad interest to Science’s readership, including microbial ecologists, molecular biologists, geologists, and astrobiologists. Our on-line submission of the manuscript (~2500 words, Microsoft Word format) also includes: 5 figures (comprising 19 separate panels); Supplementary Information (comprising Materials and Methods; References; and 4 tables, Tables S1-S4); we have sent 2 reference manuscripts in press (Levy et al. and Kowalewski et al.; PDF format), both of which are referenced in our paper, to the Washington, D.C. address. None of our suggested reviewers (listed separately) has seen this manuscript. On behalf of our co-authors and ourselves, we thank you for your consideration and look forward to hearing from you. Sincerely,

Kay Bidle and Paul Falkowski

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Suggested Reviewers:

Edward F. DeLongDepartment of Civil and Environmental Engineering77 Massachusetts Ave; 1-290Cambridge, MA 02139Office: 48-427Phone: (617) 253-5271email: delong@mit.edu

David M. KarlDepartment of Oceanography1000 Pope Rd.  MSB 629University of HawaiiHonolulu, HI  96822  Phone: (808) 956-8964 Fax: (808) 956-5059e-mail:  dkarl@hawaii.edu

Farooq AzamScripps Institution of Oceanography, UCSD9500 Gilman DriveLa Jolla CA, 92093-0202Phone: (858) 534-6850Fax: (858) 534-7313email: fazam@ucsd.edu

Bess B. WardDepartment of Ecology and Evolutionary BiologyPrinceton University, Princeton, NJ 08544-100Phone: (609) 258-5150Fax: 609.258.0796email: bbw@princeton.edu David SugdenSchool of GeosciencesThe University of EdinburghGrant InstituteThe King's BuildingsWest Mains RoadEDINBURGH EH9 3JWPhone: +44 (0) 131 650 7542Fax: +44 (0) 131 668 3184email: des@geo.ed.ac.uk 

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