Dataset Information


Transcription profiling of wild type G. sulfurreducens DL1 strain and mutant delta-sfrAB::kan, acetate-adapted strain using fumarate as an electron acceptor

ABSTRACT: 1. Summary: SfrAB, the soluble ferric reductase of Geobacter sulfurreducens, is a two subunit complex that can catalyze the NADPH-dependent reduction of chelated Fe(III) and is encoded in a two gene cluster in which the sfrB gene (GSU_0510) is 126 bp upstream of the sfrA gene (GSU_0509)[Kaufmann and Lovley (2001) J. Bacteriol. 183:4468-4476]. In order to gain insight into the physiological function of SfrAB, a knockout mutant was constructed by replacing a 3.6 kb stretch of sequence encompassing the C-terminal 72% of the SfrB and the N-terminal 80% of the SfrA coding sequences with a kanamycin resistance cassette via homologous recombination. The SfrAB knockout mutant (Delta sfrAB::kan) was found to be initially unable to grow in media in which acetate served as the sole electron donor. However, following prolonged incubation (2-3 weeks) in acetate:fumarate medium, an acetate-adapted SfrAB-null strain with the ability to grow on fumarate with acetate serving as the sole electron donor was isolated. This acetate-adapted, SfrAB-null strain and wild type G. sulfurreducens were cultured in parallel in chemostats at an intermediate growth rate (0.05 hr-1) in acetate-limited freshwater fumarate medium (5 mM acetate:27.5 mM fumarate). After the chemostats reached steady state, cells were harvested by centrifugation and RNA was extracted. In order to identify genes that were involved in growth on acetate in the absence of SfrAB, this RNA was used to perform microarray analysis comparing gene expression in the acetate-adapted, SfrAB-null and wild type strains. 2. Growth condtions: Cells were cultured in chemostats at a dilution rate of 0.05 hr-1 in acetate-limited freshwater fumarate medium (5 mM acetate:27.5 mM fumarate) and harvested when the chemostats were at steady state. 3. Mutant designation: acetate-adapted SfrAB-null strain, genotype= Delta sfrAB::kan. (Note: there is an unadapted Delta sfrAB::kan strain which cannot grow on acetate and an adapted one which can. The acetate-adapted strain was used for the microarray analysis).

ORGANISM(S): Geobacter sulfurreducens  

SUBMITTER: Barbara Methe  

PROVIDER: E-TIGR-130 | ArrayExpress | 2008-01-03


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Involvement of Geobacter sulfurreducens SfrAB in acetate metabolism rather than intracellular, respiration-linked Fe(III) citrate reduction.

Coppi Maddalena V MV   O'Neil Regina A RA   Leang Ching C   Kaufmann Franz F   Methé Barbara A BA   Nevin Kelly P KP   Woodard Trevor L TL   Liu Anna A   Lovley Derek R DR  

Microbiology (Reading, England) 20071001 Pt 10

A soluble ferric reductase, SfrAB, which catalysed the NADPH-dependent reduction of chelated Fe(III), was previously purified from the dissimilatory Fe(III)-reducing micro-organism Geobacter sulfurreducens, suggesting that reduction of chelated forms of Fe(III) might be cytoplasmic. However, metabolically active spheroplast suspensions could not catalyse acetate-dependent Fe(III) citrate reduction, indicating that periplasmic and/or outer-membrane components were required for Fe(III) citrate red  ...[more]

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