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Nanocalorimetric Characterization of Microbial Activity in Deep Subsurface Oceanic Crustal Fluids.

Nanocalorimetric Characterization of Microbial Activity in Deep Subsurface Oceanic Crustal Fluids.

Authors :
Robador, Alberto
LaRowe, Douglas E.
Nealson, Kenneth H.
Amend, Jan P.
Jungbluth, Sean P.
Huei-Ting Lin
Rappé, Michael S.
Mayumi Seto
Algar, Christopher Kenneth
Source :
Frontiers in Microbiology; 4/5/2016, p1-8, 8p
Publication Year :
2016

Abstract

Although fluids within the upper oceanic basaltic crust harbor a substantial fraction of the total prokaryotic cells on Earth, the energy needs of this microbial population are unknown. In this study, a nanocalorimeter (sensitivity down to 1.2 nW ml<superscript>-1</superscript>) was used to measure the enthalpy of microbially catalyzed reactions as a function of temperature in samples from two distinct crustal fluid aquifers. Microorganisms in unamended, warm (63°C) and geochemically altered anoxic fluids taken from 292 meters sub-basement (msb) near the Juan de Fuca Ridge produced 267.3 mJ of heat over the course of 97 h during a step-wise isothermal scan from 35.5 to 85.0°C. Most of this heat signal likely stems from the germination of thermophilic endospores (6.66 ? 104 cells ml<superscript>-1</superscript> FLUID) and their subsequent metabolic activity at temperatures greater than 50°C. The average cellular energy consumption (5.68 pW cell<superscript>-1</superscript>) reveals the high metabolic potential of a dormant community transported by fluids circulating through the ocean crust. By contrast, samples taken from 293 msb from cooler (3.8°C), relatively unaltered oxic fluids, produced 12.8 mJ of heat over the course of 14 h as temperature ramped from 34.8 to 43.0°C. Corresponding cell-specific energy turnover rates (0.18 pW cell<superscript>-1</superscript>) were converted to oxygen uptake rates of 24.5 nmol O<subscript>2</subscript> ml<superscript>-1</superscript> FLUID d<superscript>-1</superscript>, validating previous model predictions of microbial activity in this environment. Given that the investigated fluids are characteristic of expansive areas of the upper oceanic crust, the measured metabolic heat rates can be used to constrain boundaries of habitability and microbial activity in the oceanic crust. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
1664302X
Database :
Complementary Index
Journal :
Frontiers in Microbiology
Publication Type :
Academic Journal
Accession number :
114492839
Full Text :
https://doi.org/10.3389/fmicb.2016.00454