Deep subseafloor microbial cells on physiological standby

Microscopic counts of microbial cells in deep sediment cores retrieved by scientific ocean drilling have revealed the largest living ecosystem on earth: the deep biosphere (1, 2). Hidden beneath the seafloor, a large part of all prokaryotic cells on earth persist under conditions so highly energy-limited that it seems to violate the constraints to life. This deep biosphere is the most understudied ecosystem, inhabited by organisms only distantly related to known laboratory strains. It is not even clear whether the cells are alive and metabolically active, or are dormant or perhaps dead. The report by Morono et al. in PNAS (3) attacks this very basic question with new convincing experiments.

[1]  Franciszek Hasiuk,et al.  Subseafloor sedimentary life in the South Pacific Gyre , 2009, Proceedings of the National Academy of Sciences.

[2]  K. Hinrichs,et al.  Significant contribution of Archaea to extant biomass in marine subsurface sediments , 2008, Nature.

[3]  R. Parkes,et al.  Recent studies on bacterial populations and processes in subseafloor sediments: A review , 2000 .

[4]  B. Jørgensen,et al.  Prokaryotic cells of the deep sub-seafloor biosphere identified as living bacteria , 2005, Nature.

[5]  P. Price,et al.  Temperature dependence of metabolic rates for microbial growth, maintenance, and survival. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[6]  A. Driessen,et al.  Ion permeability of the cytoplasmic membrane limits the maximum growth temperature of bacteria and archaea , 1995, Molecular microbiology.

[7]  B. Jørgensen,et al.  A Starving Majority Deep Beneath the Seafloor , 2006, Science.

[8]  R. Nielsen,et al.  Ancient bacteria show evidence of DNA repair , 2007, Proceedings of the National Academy of Sciences.

[9]  K. Nealson,et al.  Microbial survival: the paleome: a sedimentary genetic record of past microbial communities. , 2005, Astrobiology.

[10]  Andrew J. Weightman,et al.  Deep sub-seafloor prokaryotes stimulated at interfaces over geological time , 2005, Nature.

[11]  A. Teske,et al.  Uncultured archaea in deep marine subsurface sediments: have we caught them all? , 2008, The ISME Journal.

[12]  Rika Anderson,et al.  Heterotrophic Archaea dominate sedimentary subsurface ecosystems off Peru. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[13]  J. Lennon,et al.  Microbial seed banks: the ecological and evolutionary implications of dormancy , 2011, Nature Reviews Microbiology.

[14]  Takeshi Terada,et al.  Carbon and nitrogen assimilation in deep subseafloor microbial cells , 2011, Proceedings of the National Academy of Sciences.

[15]  W. Whitman,et al.  Prokaryotes: the unseen majority. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[16]  J. Bada,et al.  Radiation-Dependent Limit for the Viability of Bacterial Spores in Halite Fluid Inclusions and on Mars , 2003, Radiation research.

[17]  Scott Rutherford,et al.  Metabolic Activity of Subsurface Life in Deep-Sea Sediments , 2002, Science.