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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
agricultural and biological sciences
Does aspartic acid racemization constrain the depth limit of the subsurface biosphere?
Geobiology, Volume 12, No. 1, Year 2014
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Description
Previous studies of the subsurface biosphere have deduced average cellular doubling times of hundreds to thousands of years based upon geochemical models. We have directly constrained the in situ average cellular protein turnover or doubling times for metabolically active micro-organisms based on cellular amino acid abundances, D/L values of cellular aspartic acid, and the in vivo aspartic acid racemization rate. Application of this method to planktonic microbial communities collected from deep fractures in South Africa yielded maximum cellular amino acid turnover times of ~89 years for 1 km depth and 27 °C and 1-2 years for 3 km depth and 54 °C. The latter turnover times are much shorter than previously estimated cellular turnover times based upon geochemical arguments. The aspartic acid racemization rate at higher temperatures yields cellular protein doubling times that are consistent with the survival times of hyperthermophilic strains and predicts that at temperatures of 85 °C, cells must replace proteins every couple of days to maintain enzymatic activity. Such a high maintenance requirement may be the principal limit on the abundance of living micro-organisms in the deep, hot subsurface biosphere, as well as a potential limit on their activity. The measurement of the D/L of aspartic acid in biological samples is a potentially powerful tool for deep, fractured continental and oceanic crustal settings where geochemical models of carbon turnover times are poorly constrained. Experimental observations on the racemization rates of aspartic acid in living thermophiles and hyperthermophiles could test this hypothesis. The development of corrections for cell wall peptides and spores will be required, however, to improve the accuracy of these estimates for environmental samples. © 2013 John Wiley & Sons Ltd.
Authors & Co-Authors
Onstott, Tullis C.
United States, Princeton
Princeton University
United States, Bloomington
Indiana University Bloomington
Magnabosco, Cara
United States, Princeton
Princeton University
United States, Bloomington
Indiana University Bloomington
Aubrey, Andrew D.
United States, Pasadena
Jet Propulsion Laboratory
Burton, Aaron S.
United States, Houston
Nasa Johnson Space Center
Dworkin, Jason P.
United States, Greenbelt
Nasa Goddard Space Flight Center
Elsila, Jamie E.
United States, Greenbelt
Nasa Goddard Space Flight Center
Grunsfeld, S.
United States, Clarksville
River Hill High School
Cao, B. H.
United States, Merced
Uc Merced
Hein, J. E.
United States, Merced
Uc Merced
Glavin, Daniel P.
United States, Greenbelt
Nasa Goddard Space Flight Center
Kieft, Thomas L.
United States, Socorro
New Mexico Institute of Mining and Technology
Silver, B. J.
United States, Cranbury
Arcadis
Phelps, Tommy J.
United States, Oak Ridge
Oak Ridge National Laboratory
van Heerden, Esta
South Africa, Bloemfontein
University of the Free State
Opperman, Diederik Johannes
South Africa, Bloemfontein
University of the Free State
Bada, Jeffrey L.
United States, La Jolla
Scripps Institution of Oceanography
Statistics
Citations: 57
Authors: 16
Affiliations: 12
Identifiers
Doi:
10.1111/gbi.12069
ISSN:
14724677
e-ISSN:
14724669
Research Areas
Environmental
Violence And Injury
Study Locations
South Africa