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Title: Metabolic Processes Account for the Majority of Intracellular Water in Log-Phase Escherichia coli Cells as Revealed by Hydrogen Isotopes

Abstract

It is generally believed that water transport across biological membranes is essentially a near-instantaneous process, with water molecules diffusing directly across the membrane as well as through pores such as aquaporins. As a result of these processes by which water can equilibrate across a membrane, a common assumption is that intracellular water is indistinguishable from extracellular water. To test this assumption directly, we measured the hydrogen isotope ratio of intracellular water in Escherichia coli cells. Our results demonstrate that over 50% of the intracellular water hydrogen atoms in log-phase E. coli cells are isotopically distinct from the growth medium water and that these isotopically distinct hydrogen atoms are derived from metabolic processes. As expected, the H/D isotope ratio of intracellular water from log-phase cells showed an appreciably larger contribution from metabolic water than did intracellular water from stationary-phase cells (53 ± 12% versus 23 ± 5%). The H/D isotope ratio of intracellular water was also monitored indirectly by measuring the isotope ratio of fatty acids, metabolites that are known to incorporate hydrogen atoms from water during biosynthesis. Significantly, the difference in the isotopic composition of intracellular water from log- to stationary-phase E. coli cells was reflected in the hydrogen isotopemore » ratio of individual fatty acids harvested at the two different times, indicating that the isotope ratio of metabolites can be used as an indirect probe of metabolic activity. Together these results demonstrate that contrary to the common assumption that intracellular water is identical to extracellular water, these two pools of water can actually be quite distinct.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
944783
Report Number(s):
PNNL-SA-49820
TRN: US200902%%949
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemistry, 45(45):13622-13630; Journal Volume: 45; Journal Issue: 45
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ATOMS; BIOSYNTHESIS; CARBOXYLIC ACIDS; ESCHERICHIA COLI; HYDROGEN; HYDROGEN ISOTOPES; ISOTOPE RATIO; MEMBRANES; METABOLITES; PROBES; TRANSPORT; WATER; intracellular water; Escherichia coli cells; metobolic process

Citation Formats

Kreuzer-Martin, Helen W., Lott, Michael J., Ehleringer, James, and Hegg, Eric. Metabolic Processes Account for the Majority of Intracellular Water in Log-Phase Escherichia coli Cells as Revealed by Hydrogen Isotopes. United States: N. p., 2006. Web. doi:10.1021/bi0609164.
Kreuzer-Martin, Helen W., Lott, Michael J., Ehleringer, James, & Hegg, Eric. Metabolic Processes Account for the Majority of Intracellular Water in Log-Phase Escherichia coli Cells as Revealed by Hydrogen Isotopes. United States. doi:10.1021/bi0609164.
Kreuzer-Martin, Helen W., Lott, Michael J., Ehleringer, James, and Hegg, Eric. Sun . "Metabolic Processes Account for the Majority of Intracellular Water in Log-Phase Escherichia coli Cells as Revealed by Hydrogen Isotopes". United States. doi:10.1021/bi0609164.
@article{osti_944783,
title = {Metabolic Processes Account for the Majority of Intracellular Water in Log-Phase Escherichia coli Cells as Revealed by Hydrogen Isotopes},
author = {Kreuzer-Martin, Helen W. and Lott, Michael J. and Ehleringer, James and Hegg, Eric},
abstractNote = {It is generally believed that water transport across biological membranes is essentially a near-instantaneous process, with water molecules diffusing directly across the membrane as well as through pores such as aquaporins. As a result of these processes by which water can equilibrate across a membrane, a common assumption is that intracellular water is indistinguishable from extracellular water. To test this assumption directly, we measured the hydrogen isotope ratio of intracellular water in Escherichia coli cells. Our results demonstrate that over 50% of the intracellular water hydrogen atoms in log-phase E. coli cells are isotopically distinct from the growth medium water and that these isotopically distinct hydrogen atoms are derived from metabolic processes. As expected, the H/D isotope ratio of intracellular water from log-phase cells showed an appreciably larger contribution from metabolic water than did intracellular water from stationary-phase cells (53 ± 12% versus 23 ± 5%). The H/D isotope ratio of intracellular water was also monitored indirectly by measuring the isotope ratio of fatty acids, metabolites that are known to incorporate hydrogen atoms from water during biosynthesis. Significantly, the difference in the isotopic composition of intracellular water from log- to stationary-phase E. coli cells was reflected in the hydrogen isotope ratio of individual fatty acids harvested at the two different times, indicating that the isotope ratio of metabolites can be used as an indirect probe of metabolic activity. Together these results demonstrate that contrary to the common assumption that intracellular water is identical to extracellular water, these two pools of water can actually be quite distinct.},
doi = {10.1021/bi0609164},
journal = {Biochemistry, 45(45):13622-13630},
number = 45,
volume = 45,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}