title: Mechanistic stratification in electroactive biofilms of Geobacter sulfurreducens mediated by pilus nanowires.
abstract: Electricity generation by Geobacter sulfurreducens biofilms grown on electrodes involves matrix-associated electron carriers, such as c-type cytochromes. Yet, the contribution of the biofilm's conductive pili remains uncertain, largely because pili-defective mutants also have cytochrome defects. Here we report that a pili-deficient mutant carrying an inactivating mutation in the pilus assembly motor PilB has no measurable defects in cytochrome expression, yet forms anode biofilms with reduced electroactivity and is unable to grow beyond a threshold distance (∼10 μm) from the underlying electrode. The defects are similar to those of a Tyr3 mutant, which produces poorly conductive pili. The results support a model in which the conductive pili permeate the biofilms to wire the cells to the conductive biofilm matrix and the underlying electrode, operating coordinately with cytochromes until the biofilm reaches a threshold thickness that limits the efficiency of the cytochrome pathway but not the functioning of the conductive pili network.
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, 567 Wilson Road, Rm 6190, Biomedical and Physical Science building, East Lansing, Michigan 48824, USA.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Steidl
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, 567 Wilson Road, Rm 6190, Biomedical and Physical Science building, East Lansing, Michigan 48824, USA.
authors.forename: Sanela
authors.initials: S
authors.lastname: Lampa-Pastirk
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, 567 Wilson Road, Rm 6190, Biomedical and Physical Science building, East Lansing, Michigan 48824, USA.
authors.forename: Gemma
authors.initials: G
authors.lastname: Reguera
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001674:Bioelectric Energy Sources; D018441:Biofilms; D003580:Cytochromes / Q000378:metabolism; D004566:Electrodes; D004579:Electron Transport / Q000502:physiology*; D010861:Fimbriae, Bacterial / Q000502:physiology*; D045302:Geobacter / Q000502:physiology*; D009154:Mutation; D053770:Nanowires; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003580:Cytochromes; D010088:Oxidoreductases; C068255:pilB protein, Bacteria