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Journal of Bacteriology, January 2006, p. 702-710, Vol. 188, No. 2
0021-9193/06/$08.00+0 doi:10.1128/JB.188.2.702-710.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Lingyun Li,2,
Tomas Rejtar,2
Daniel J. Lessner,1
Barry L. Karger,2* and
James G. Ferry1*
Department of Biochemistry and Molecular Biology, and Center for Microbial Structural Biology, 205 South Frear Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802,1 Barnett Institute and Department of Chemistry, Northeastern University, Boston, Massachusetts 021152
Received 28 June 2005/ Accepted 6 October 2005
A liquid chromatography-hybrid linear ion trap-Fourier transform ion cyclotron resonance mass spectrometry approach was used to determine the differential abundance of proteins in acetate-grown cells compared to that of proteins in methanol-grown cells of the marine isolate Methanosarcina acetivorans metabolically labeled with 14N versus 15N. The 246 differentially abundant proteins in M. acetivorans were compared with the previously reported 240 differentially expressed genes of the freshwater isolate Methanosarcina mazei determined by transcriptional profiling of acetate-grown cells compared to methanol-grown cells. Profound differences were revealed for proteins involved in electron transport and energy conservation. Compared to methanol-grown cells, acetate-grown M. acetivorans synthesized greater amounts of subunits encoded in an eight-gene transcriptional unit homologous to operons encoding the ion-translocating Rnf electron transport complex previously characterized from the Bacteria domain. Combined with sequence and physiological analyses, these results suggest that M. acetivorans replaces the H2-evolving Ech hydrogenase complex of freshwater Methanosarcina species with the Rnf complex, which generates a transmembrane ion gradient for ATP synthesis. Compared to methanol-grown cells, acetate-grown M. acetivorans synthesized a greater abundance of proteins encoded in a seven-gene transcriptional unit annotated for the Mrp complex previously reported to function as a sodium/proton antiporter in the Bacteria domain. The differences reported here between M. acetivorans and M. mazei can be attributed to an adaptation of M. acetivorans to the marine environment.
Supplemental material for this article may be found at http://jb.asm.org/.
Q.L. and L.L. contributed equally.
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