title: In situ measurement of Fe(III) reduction activity of Geobacter pelophilus by simultaneous in situ RT-PCR and XPS analysis.
abstract: Geobacter pelophilus is capable of dissimilatory Fe(III)-reduction on solid phase Fe(III)-oxides by means of surface attachment and direct electron transport to Fe(III), in part mediated by outer membrane c-type cytochromes. A study was undertaken to characterize surface colonization patterns, gene expression, and mineral transformation by this organism. The gene ferA (Geobacter sulfurreducens outer membrane Fe(III) reductase cytochrome c) was used as a target for PCR based molecular detection methods for visualizing G. pelophilus surface colonization. Protein extracts were prepared from solid-phase cultures, and cytochrome c content assessed. Mineral transformations were followed by X-ray photoelectron spectroscopy (XPS). Results of in situ (IS) RT-PCR experiments demonstrate that G. pelophilus attaches and grows at ferrihydrite mineral surfaces. Fluorescently-labeled cells were observed after IS-RT-PCR experiments, suggesting that G. pelophilus contains a cytochrome c sequence similar to ferA in G. sulfurreducens which is expressed in the presence of ferrihydrite. Protein extracts possessed high mass c-type cytochromes of similar size to those found in G. sulfurreducens. In addition, unique high-mass c-type cytochromes were also detected. XPS analysis demonstrated mineral transformation to occur, mediated by the surface associated population. This study demonstrates that G. pelophilus attaches to Fe(III)-oxide surfaces, reduces the Fe(III) oxides at the surface, produces c-type cytochromes under these growth conditions, and expresses cytochrome c-encoding genes as measured by in situ molecular detection techniques.
authors.affiliation: Department of Microbiology and Savannah River Ecology Laboratory, University of Georgia, Athens, GA 30602, USA.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Neal
authors.forename: Lani K
authors.initials: LK
authors.lastname: Clough
authors.forename: Todd D
authors.initials: TD
authors.lastname: Perkins
authors.forename: Brenda J
authors.initials: BJ
authors.lastname: Little
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Magnuson
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D045302:Geobacter / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013052:Spectrometry, X-Ray Emission
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D005290:Ferric Compounds; D012329:RNA, Bacterial; C092844:ferric oxyhydroxide