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In situ measurement of Fe(III) reduction activity of Geobacter pelophilus by simultaneous in situ RT-PCR and XPS analysis (2004)

Neal, Andrew L. ; Clough, Lani K. ; Perkins, Todd D. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

FEMS microbiology ecology 49 (2004), S. 0

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ISSN: 1574-6941

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 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.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1016/j.femsec.2004.03.014

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Advantages of environmental scanning electron microscopy in studies of microorganisms (1993)

Collins, Scott P. ; Pope, Robert K. ; Scheetz, Raymond W. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Microscopy Research and Technique 25 (1993), S. 398-405

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ISSN: 1059-910X

Keywords: Environmental scanning electron microscopy ; Algae ; Fungi ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Natural Sciences in General

Notes: Microorganisms, including bacteria, fungi, protozoa, and microalgae, are composed predominantly of water which prohibits direct observation in a traditional scanning electron microscope (SEM). Preparation for SEM requires that microorganisms be fixed, frozen or dehydrated, and coated with a conductive film before observation in a high vacuum environment. Sample preparation may mechanically disturb delicate samples, compromise morphological information, and introduce other artifacts. The environmental scanning electron microscope (ESEM) provides a technology for imaging hydrated or dehydrated biological samples with minimal manipulation and without the need for conductive coatings.Sporulating cultures of three fungi, Aspergillus sp., Cunninghamella sp., and Mucor sp., were imaged in the ESEM to assess usefulness of the instrument in the direct observation of delicate, uncoated, biological specimens. Asexual sporophores showed no evidence of conidial displacement or disruption of sporangia.Uncoated algal cells of Euglena gracilis and Spirogyra sp. were examined using the backscatter electron detector (BSE) and the environmental secondary electron detector (ESD) of the ESEM. BSE images had more clearly defined intracellular structures, whereas ESD gave a clearer view of the surface. E. gracilis cells fixed with potassium permanganate, Spirogyra sp. stained with Lugol's solution, and Saprolegnia sp. fixed with osmium tetroxide were compared using BSE and ESD to demonstrate that cellular details could be enhanced by the introduction of heavy metals. The effect of cellular water on signal quality was evaluated by comparing hydrated to critical point dried specimens. © 1993 Wiley-Liss, Inc.

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