Genes for two multicopper proteins required for Fe(III) oxide reduction in Geobacter sulfurreducens have different expression patterns both in the subsurface and on energy-harvesting electrodes.
Previous studies have shown that Geobacter sulfurreducens requires the outer-membrane, multicopper protein OmpB for Fe(III) oxide reduction. A homologue of OmpB, designated OmpC, which is 36 % similar to OmpB, has been discovered in the G. sulfurreducens genome. Deletion of ompC inhibited reduction of insoluble, but not soluble Fe(III). Analysis of multiple Geobacter and Pelobacter genomes, as well as in situ Geobacter, indicated that genes encoding multicopper proteins are conserved in Geobacter species but are not found in Pelobacter species. Levels of ompB transcripts were similar in G. sulfurreducens at different growth rates in chemostats and during growth on a microbial fuel cell anode. In contrast, ompC transcript levels increased at higher growth rates in chemostats and with increasing current production in fuel cells. Constant levels of Geobacter ompB transcripts were detected in groundwater during a field experiment in which acetate was added to the subsurface to promote in situ uranium bioremediation. In contrast, ompC transcript levels increased during the rapid phase of growth of Geobacter species following addition of acetate to the groundwater and then rapidly declined. These results demonstrate that more than one multicopper protein is required for optimal Fe(III) oxide reduction in G. sulfurreducens and suggest that, in environmental studies, quantifying OmpB/OmpC-related genes could help alleviate the problem that Pelobacter genes may be inadvertently quantified via quantitative analysis of 16S rRNA genes. Furthermore, comparison of differential expression of ompB and ompC may provide insight into the in situ metabolic state of Geobacter species in environments of interest.
Holmes
Dawn E
DE
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Mester
Tünde
T
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
O'Neil
Regina A
RA
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Perpetua
Lorrie A
LA
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Larrahondo
M Juliana
MJ
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Glaven
Richard
R
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Sharma
Manju L
ML
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Ward
Joy E
JE
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Nevin
Kelly P
KP
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Lovley
Derek R
DR
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
D000085:Acetates / Q000378:metabolism; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D004566:Electrodes / Q000382:microbiology*; D005290:Ferric Compounds / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D045302:Geobacter / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010802:Phylogeny; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D012988:Soil Microbiology; D014501:Uranium / Q000378:metabolism
D000085:Acetates; D001425:Bacterial Outer Membrane Proteins; D005290:Ferric Compounds; C000499:ferric oxide; D014501:Uranium