title: Electroactivity of phototrophic river biofilms and constitutive cultivable bacteria.
abstract: Electroactivity is a property of microorganisms assembled in biofilms that has been highlighted in a variety of environments. This characteristic was assessed for phototrophic river biofilms at the community scale and at the bacterial population scale. At the community scale, electroactivity was evaluated on stainless steel and copper alloy coupons used both as biofilm colonization supports and as working electrodes. At the population scale, the ability of environmental bacterial strains to catalyze oxygen reduction was assessed by cyclic voltammetry. Our data demonstrate that phototrophic river biofilm development on the electrodes, measured by dry mass and chlorophyll a content, resulted in significant increases of the recorded potentials, with potentials of up to +120 mV/saturated calomel electrode (SCE) on stainless steel electrodes and +60 mV/SCE on copper electrodes. Thirty-two bacterial strains isolated from natural phototrophic river biofilms were tested by cyclic voltammetry. Twenty-five were able to catalyze oxygen reduction, with shifts of potential ranging from 0.06 to 0.23 V, cathodic peak potentials ranging from -0.36 to -0.76 V/SCE, and peak amplitudes ranging from -9.5 to -19.4 μA. These isolates were diversified phylogenetically (Actinobacteria, Firmicutes, Bacteroidetes, and Alpha-, Beta-, and Gammaproteobacteria) and exhibited various phenotypic properties (Gram stain, oxidase, and catalase characteristics). These data suggest that phototrophic river biofilm communities and/or most of their constitutive bacterial populations present the ability to promote electronic exchange with a metallic electrode, supporting the following possibilities: (i) development of electrochemistry-based sensors allowing in situ phototrophic river biofilm detection and (ii) production of microbial fuel cell inocula under oligotrophic conditions.
authors.affiliation: Université de Toulouse, UPS, INP, Laboratoire d’Ecologie Fonctionnelle, 118 Route de Narbonne, F-31062 Toulouse, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Lyautey
authors.forename: Amandine
authors.initials: A
authors.lastname: Cournet
authors.forename: Soizic
authors.initials: S
authors.lastname: Morin
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Boulêtreau
authors.forename: Luc
authors.initials: L
authors.lastname: Etcheverry
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Charcosset
authors.forename: François
authors.initials: F
authors.lastname: Delmas
authors.forename: Alain
authors.initials: A
authors.lastname: Bergel
authors.forename: Frédéric
authors.initials: F
authors.lastname: Garabetian
mesh_terms: D001419:Bacteria / Q000302:isolation & purification / Q000378:metabolism; D018407:Bacterial Physiological Phenomena; D001674:Bioelectric Energy Sources / Q000382:microbiology; D018441:Biofilms; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D003300:Copper; D004560:Electricity; D004563:Electrochemistry; D004566:Electrodes / Q000382:microbiology; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D018524:Phototropism; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics; D045483:Rivers / Q000382:microbiology*; D012623:Seawater / Q000382:microbiology; D013193:Stainless Steel
chemical_list: D012336:RNA, Ribosomal, 16S; D013193:Stainless Steel; D002734:Chlorophyll; D003300:Copper; D010100:Oxygen; D000077194:Chlorophyll A