TY  - JOUR
A1  - Kallmeyer, Jens
A1  - Pockalny, Robert
A1  - Adhikari, Rishi Ram
A1  - Smith, David C.
A1  - D'Hondt, Steven
T1  - Global distribution of microbial abundance and biomass in subseafloor sediment
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - The global geographic distribution of subseafloor sedimentary microbes and the cause(s) of that distribution are largely unexplored. Here, we show that total microbial cell abundance in subseafloor sediment varies between sites by ca. five orders of magnitude. This variation is strongly correlated with mean sedimentation rate and distance from land. Based on these correlations, we estimate global subseafloor sedimentary microbial abundance to be 2.9 center dot 10(29) cells [corresponding to 4.1 petagram (Pg) C and similar to 0.6% of Earth's total living biomass]. This estimate of subseafloor sedimentary microbial abundance is roughly equal to previous estimates of total microbial abundance in seawater and total microbial abundance in soil. It is much lower than previous estimates of subseafloor sedimentary microbial abundance. In consequence, we estimate Earth's total number of microbes and total living biomass to be, respectively, 50-78% and 10-45% lower than previous estimates.
KW  - deep biosphere
KW  - cell enumeration
KW  - global microbial biomass
KW  - subsurface life
Y1  - 2012
U6  - https://doi.org/10.1073/pnas.1203849109
SN  - 0027-8424
VL  - 109
IS  - 40
SP  - 16213
EP  - 16216
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kallmeyer, Jens
A1  - Smith, David C.
T1  - An improved electroelution method for separation of DNA from humic substances in marine sediment DNA extracts
N2  - We present a method for the rapid and simple extraction of DNA from marine sediments using electroelution. It effectively separates DNA from compounds, including humic substances, that interfere with subsequent DNA quantification and amplification. After extraction of the DNA from the sediment into an aqueous solution, the crude sample is encased in 2% agarose gel and exposed to an electrical current, which draws the DNA out of the gel into a centrifugal filter vial. After electroelution, the sample is centrifuged to remove contaminants <= 100 000 Da. Recovery of DNA using this method is quantitative and does not discriminate on the basis of size, as determined using DNA standards and DNA extracts from environmental samples. Amplification of DNA is considerably improved due to removal of PCR inhibitors. For Archaea, only these purified extracts yielded PCR products. This method allows for the use of relatively large volumes of sediment and is particularly useful for sediments containing low biomass such as deeply buried marine sediments. It works with both organic-rich and -poor sediment, as well as with sediment where calcium carbonate is abundant and sediment where it is limited; consequently, adjustment of protocols is unnecessary for samples with very different organic and mineral contents.
Y1  - 2009
UR  - http://www3.interscience.wiley.com/cgi-bin/issn?DESCRIPTOR=PRINTISSN&VALUE=0168-6496
U6  - https://doi.org/10.1111/j.1574-6941.2009.00684.x
SN  - 0168-6496
ER  - 
TY  - JOUR
A1  - D'Hondt, Steven
A1  - Spivack, Arthur J.
A1  - Pockalny, Robert
A1  - Ferdelman, Timothy G.
A1  - Fischer, Jan P.
A1  - Kallmeyer, Jens
A1  - Abrams, Lewis J.
A1  - Smith, David C.
A1  - Graham, Dennis
A1  - Hasiuk, Franciszek
A1  - Schrum, Heather
A1  - Stancin, Andrea M.
T1  - Subseafloor sedimentary life in the South Pacific Gyre
N2  - The low-productivity South Pacific Gyre (SPG) is Earth's largest oceanic province. Its sediment accumulates extraordinarily slowly (0.1-1 m per million years). This sediment contains a living community that is characterized by very low biomass and very low metabolic activity. At every depth in cored SPG sediment, mean cell abundances are 3 to 4 orders of magnitude lower than at the same depths in all previously explored subseafloor communities. The net rate of respiration by the subseafloor sedimentary community at each SPG site is 1 to 3 orders of magnitude lower than the rates at previously explored sites. Because of the low respiration rates and the thinness of the sediment, interstitial waters are oxic throughout the sediment column in most of this region. Consequently, the sedimentary community of the SPG is predominantly aerobic, unlike previously explored subseafloor communities. Generation of H-2 by radiolysis of water is a significant electron-donor source for this community. The per-cell respiration rates of this community are about 2 orders of magnitude higher (in oxidation/reduction equivalents) than in previously explored anaerobic subseafloor communities. Respiration rates and cell concentrations in subseafloor sediment throughout almost half of the world ocean may approach those in SPG sediment.
Y1  - 2009
UR  - http://www.pnas.org/
U6  - https://doi.org/10.1073/pnas.0811793106
SN  - 0027-8424
ER  -