INSTITUTE OF MARINE & COASTAL SCIENCES
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Dr. Kay D. Bidle
Assistant Professor
x 393
Fax: 732-932-4083
bidle@marine.rutgers.edu
H. Jesse Smith
Senior Editor
Science
1200 New York Avenue NW
Washington, DC 20005
202-326-6556
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
R U T G E R S, T H E S T A T E U N I V E R S I T Y O F N E W J E R S E Y
Suggested Reviewers:
Edward F. DeLong
Department of Civil and Environmental Engineering
77 Massachusetts Ave; 1-290
Cambridge, MA 02139
Office: 48-427
Phone: (617) 253-5271
email: delong@mit.edu
David M. Karl
Department of Oceanography
1000 Pope Rd. MSB 629
University of Hawaii
Honolulu, HI 96822
Phone: (808) 956-8964
Fax: (808) 956-5059
e-mail: dkarl@hawaii.edu
Farooq Azam
Scripps Institution of Oceanography, UCSD
9500 Gilman Drive
La Jolla CA, 92093-0202
Phone: (858) 534-6850
Fax: (858) 534-7313
email: fazam@ucsd.edu
Bess B. Ward
Department of Ecology and Evolutionary Biology
Princeton University, Princeton, NJ 08544-100
Phone: (609) 258-5150
Fax: 609.258.0796
email: bbw@princeton.edu
David Sugden
School of Geosciences
The University of Edinburgh
Grant Institute
The King's Buildings
West Mains Road
EDINBURGH EH9 3JW
Phone: +44 (0) 131 650 7542
Fax: +44 (0) 131 668 3184
email: des@geo.ed.ac.uk
R U T G E R S, T H E S T A T E U N I V E R S I T Y O F N E W J E R S E Y