title: Ancient bacteria show evidence of DNA repair.
abstract: Recent claims of cultivable ancient bacteria within sealed environments highlight our limited understanding of the mechanisms behind long-term cell survival. It remains unclear how dormancy, a favored explanation for extended cellular persistence, can cope with spontaneous genomic decay over geological timescales. There has been no direct evidence in ancient microbes for the most likely mechanism, active DNA repair, or for the metabolic activity necessary to sustain it. In this paper, we couple PCR and enzymatic treatment of DNA with direct respiration measurements to investigate long-term survival of bacteria sealed in frozen conditions for up to one million years. Our results show evidence of bacterial survival in samples up to half a million years in age, making this the oldest independently authenticated DNA to date obtained from viable cells. Additionally, we find strong evidence that this long-term survival is closely tied to cellular metabolic activity and DNA repair that over time proves to be superior to dormancy as a mechanism in sustaining bacteria viability.
authors.affiliation: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 54-810, Cambridge, MA 02139, USA.
authors.forename: Sarah Stewart
authors.initials: SS
authors.lastname: Johnson
authors.forename: Martin B
authors.initials: MB
authors.lastname: Hebsgaard
authors.forename: Torben R
authors.initials: TR
authors.lastname: Christensen
authors.forename: Mikhail
authors.initials: M
authors.lastname: Mastepanov
authors.forename: Rasmus
authors.initials: R
authors.lastname: Nielsen
authors.forename: Kasper
authors.initials: K
authors.lastname: Munch
authors.forename: Tina
authors.initials: T
authors.lastname: Brand
authors.forename: M Thomas P
authors.initials: MT
authors.lastname: Gilbert
authors.forename: Maria T
authors.initials: MT
authors.lastname: Zuber
authors.forename: Michael
authors.initials: M
authors.lastname: Bunce
authors.forename: Regin
authors.initials: R
authors.lastname: Rønn
authors.forename: David
authors.initials: D
authors.lastname: Gilichinsky
authors.forename: Duane
authors.initials: D
authors.lastname: Froese
authors.forename: Eske
authors.initials: E
authors.lastname: Willerslev
mesh_terms: D001419:Bacteria / Q000235:genetics*; D001483:Base Sequence; D004260:DNA Repair / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics*; D005784:Gene Amplification / Q000235:genetics; D008969:Molecular Sequence Data; D012988:Soil Microbiology
chemical_list: D004269:DNA, Bacterial