title: PilR, a transcriptional regulator for pilin and other genes required for Fe(III) reduction in Geobacter sulfurreducens.
abstract: Growth using Fe(III) as a terminal electron acceptor is a critical physiological process in Geobacter sulfurreducens. However, the mechanisms of electron transfer during Fe(III) reduction are only now being understood. It has been demonstrated that the pili in G. sulfurreducens function as microbial nanowires conducting electrons onto Fe(III) oxides. A number of c-type cytochromes have also been shown to play important roles in Fe(III) reduction. However, the regulatory networks controlling the expression of the genes involved in such processes are not well known. Here we report that the expression of pilA, which encodes the pilistructural protein, is directly regulated by a two-component regulatory system in which PilR functions as an RpoN-dependent enhancer binding protein. Surprisingly, a deletion of the pilR gene affected not only insoluble Fe(III) reduction, which requires pili, but also soluble Fe(III) reduction, which, in contrast, does not require pili. Gene expression profiling using whole-genome DNA microarray and quantitative RT-PCR analyses obtained with a PilR-deficient mutant revealed that the expression of pilA and other pilin-related genes are downregulated, while many c-type cytochromes involved in Fe(III) reduction were differentially regulated. This is the first instance of an enhancer binding protein implicated in regulating genes involved in Fe(III) respiratory functions.
authors.affiliation: Department of Microbiology, University of Massachusetts Amherst, Amherst, MA, USA. katy@ibt.unam.mx
authors.forename: Katy
authors.initials: K
authors.lastname: Juárez
authors.forename: Byoung-Chan
authors.initials: BC
authors.lastname: Kim
authors.forename: Kelly
authors.initials: K
authors.lastname: Nevin
authors.forename: Leticia
authors.initials: L
authors.lastname: Olvera
authors.forename: Gemma
authors.initials: G
authors.lastname: Reguera
authors.forename: Derek R
authors.initials: DR
authors.lastname: Lovley
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Methé
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator / Q000235:genetics; D045302:Geobacter / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D010084:Oxidation-Reduction; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D005290:Ferric Compounds; D036781:Fimbriae Proteins