HR: 0800h
AN: B21A-1021    [Abstracts]
TI: Fractionation of Carbon Isotopes in Biosynthesis of Fatty Acids by A Piezophilic Bacterium Moritella Japonica DSK1
AU: * Fang, J
EM: jsfang@iastate.edu
AF: Iowa State University, Department of Geological and Atmospheric Sciences, Ames, IA 50011
AU: Uhle, M
EM: muhle@nas.edu
AF: University of Tennessee, Department of Earth and Planetary Sciences, Knoxville, TN 37996
AU: Bartlett, D
EM: dbartlett@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, La Jolla, CA 92093
AU: Kato, C
EM: chiakik@kd5.so-net.ne.jp
AF: Extremobiosphere Research Center, Japan Agency for Earth and Marine Research, Yokosuka, 237-0061 Japan
AB: We examined stable carbon isotope fractionation in biosynthesis of fatty acids of a piezophilic bacterium Moritella japonica DSK1. DSK1 was grown to stationary phase at pressures of 0.1, 10, 20, and 50 MPa in media prepared using natural seawater supplied with glucose with the sole carbon source. DSk1 synthesized typical bacterial fatty acids (C14-19 saturated, monounsaturated, and cyclopropane fatty acids) as well as long-chain polyunsaturated fatty acids (PUFA) (20:6ω3). Bacterial cell biomass and individual fatty acids exhibited consistent pressure-dependent carbon isotope fractionations relative to glucose. The observed Δδ_FA-glucose (-1.0 to -11.9%) at 0.1 MPa was comparable to or slightly higher than fractionations reported on surface bacteria. However, Bulk biomass and fatty acids became more depleted in ¹³C with pressure. Average carbon isotope fractionation Δδ_FA-glucose) at high pressures was much higher than that for surface bacteria: -15.7, -15.3, and -18.3‰ at 10, 20, and 50 MPa, respectively. PUFA were more ¹³C depleted than saturated and monounsaturated fatty acids at all pressures. The observed isotope effects may be ascribed to the kinetics of enzymatic reactions affected by hydrostatic pressure and to different biosynthetic pathways for short-chain and long-chain fatty acids. Our results have important implications for marine biogeochemistry. The 13C depleted fatty acids in marine sediments and water column may be derived simply from piezophilic bacteria resynthesis of organic matter, not from bacterial utilization of a ¹³C-depleted carbon source (i.e., methane). The interpretation of carbon isotope signatures of marine lipids must be based on principles derived from piezophilic bacteria.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0456 Life in extreme environments
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 4870 Stable isotopes (0454, 1041)
SC: Biogeosciences [B]
MN: Fall Meeting 2005