biofilms are common in chronic wound infections and recalcitrant to treatment. Survival of cells within oxygen-limited regions in these biofilms is enabled by extracellular electron transfer (EET), whereby small redox active molecules act as electron shuttles to access distal oxidants. Here, we report that electrochemically controlling the redox state of these electron shuttles, specifically pyocyanin (PYO), can impact cell survival within anaerobic biofilms and can act synergistically with antibiotic treatment.
View Article and Find Full Text PDFA strain of Geobacter sulfurreducens, an organism capable of respiring solid extracellular substrates, lacking four of five outer membrane cytochrome complexes ( strain) grows faster and produces greater current density than the wild type grown under identical conditions. To understand cellular and biofilm modifications in the strain responsible for this increased performance, biofilms grown using electrodes as terminal electron acceptors were sectioned and imaged using electron microscopy to determine changes in thickness and cell density, while parallel biofilms incubated in the presence of nitrogen and carbon isotopes were analyzed using NanoSIMS (nanoscale secondary ion mass spectrometry) to quantify and localize anabolic activity. Long-distance electron transfer parameters were measured for wild-type and biofilms spanning 5-μm gaps.
View Article and Find Full Text PDFRedox cycling of extracellular electron shuttles can enable the metabolic activity of subpopulations within multicellular bacterial biofilms that lack direct access to electron acceptors or donors. How these shuttles catalyze extracellular electron transfer (EET) within biofilms without being lost to the environment has been a long-standing question. Here, we show that phenazines mediate efficient EET through interactions with extracellular DNA (eDNA) in Pseudomonas aeruginosa biofilms.
View Article and Find Full Text PDFMetal-reducing bacteria direct electrons to their outer surfaces, where insoluble metal oxides or electrodes act as terminal electron acceptors, generating electrical current from anaerobic respiration. is a commonly enriched electricity-producing organism, forming thick conductive biofilms that magnify total activity by supporting respiration of cells not in direct contact with electrodes. Hypotheses explaining why these biofilms fail to produce higher current densities suggest inhibition by formation of pH, nutrient, or redox potential gradients; but these explanations are often contradictory, and a lack of direct measurements of cellular growth within biofilms prevents discrimination between these models.
View Article and Find Full Text PDFAt least five gene clusters in the genome encode putative "electron conduits" implicated in electron transfer across the outer membrane, each containing a periplasmic multiheme -type cytochrome, integral outer membrane anchor, and outer membrane redox lipoprotein(s). Markerless single-gene-cluster deletions and all possible multiple-deletion combinations were constructed and grown with soluble Fe(III) citrate, Fe(III) and Mn(IV) oxides, and graphite electrodes poised at +0.24 V and -0.
View Article and Find Full Text PDFgenerates electrical current by coupling intracellular oxidation of organic acids to the reduction of proteins on the cell surface that are able to interface with electrodes. This ability is attributed to the bacterium's capacity to respire other extracellular electron acceptors that require contact, such as insoluble metal oxides. To directly investigate the genetic basis of electrode-based respiration, we constructed transposon-insertion sequencing (Tn-Seq) libraries for growth, with soluble fumarate or an electrode as the electron acceptor.
View Article and Find Full Text PDF