Electrochemical checking of aerobic isolates from electrochemically active biofilms formed in compost

Abstract

Aims: To design a cyclic voltammetry (CV) procedure to check the electrochemical activity of bacterial isolates that may explain the electrochemical properties of biofilms formed in compost. Methods and Results: Bacteria catalysing acetate oxidation in garden compost were able to form electrochemically active biofilms by transferring electrons to an electrode under chronoamperometry. They were recovered from the electrode surface and identification of the isolates using 16S rRNA sequencing showed that most of them were Gammaproteobacteria, mainly related to Enterobacter and Pseudomonas spp. A CV procedure was designed to check the electrochemical activity of both groups of isolates. Preliminary CVs suggested that the bacteria were not responsible for the catalysis of acetate oxidation. In contrast, both groups of isolates were found to catalyse the electrochemical reduction of oxygen under experimental conditions that favoured adsorption of the microbial cells on the electrode surface. Conclusions: Members of the genera Enterobacter and Pseudomonas were found to be able to catalyse the electrochemical reduction of oxygen. Significance and Impact of the Study: This study has shown the unexpected efficiency of Enterobacter and Pseudomonas spp. in catalysing the reduction of oxygen, suggesting a possible involvement of these species in biocorrosion, or possible application of these strains in designing bio‐cathode for microbial fuel cells.

Electroactivity of Phototrophic River Biofilms and Constitutive Cultivable Bacteria

“…However, the bacterial strains isolated were diversified and belonged to commonly reported phylogenetic groups for this kind of assemblage (7), although discrepancies between phenotypic characteristics and phylogenetic identification suggest that strain affiliation could be defined more accurately. Shifts of potential, peak amplitudes, and peak potentials were in the ranges of those observed for bacterial strains isolated from seawater biofilms and for reference or clinical strains by use of the same approach (13,50,51). The strains shown to be able to catalyze the electrochemical reduction of oxygen not only belonged to different phylogenetic groups but also were Gram, catalase, and oxidase positive or negative for all three, confirming recent outcomes (13,62).…”

Accelerated Reduction of Chlorinated Nitroaromatic Antibiotic Chloramphenicol by Biocathode

“…The microbial community in the cathode biofilm was different from the inoculated culture. 36,55,56 Some strains of Pseudomonas spp. appeared in both the inoculum and cathode biofilm, which were also reported to reduce nitroaromatic compounds with nitroreductase 54 and could directly uptake electron from the electrode for nitrate and sulfate reduction.…”

Monophyletic group of unclassified γ- Proteobacteria dominates in mixed culture biofilm of high-performing oxygen reducing biocathode

“…Therefore we decided to label the found sequences as belonging to unclassified γ-Proteobacteria until a more permanent taxonomy has been settled. Some bacterial genera that have already been described to be connected with oxygen reducing biofilms, like Enterobacter, Pseudomonas [17], or Acidovorax, Acinetobacter [19] as well as Desulfobulbus [43], were present only in minor amounts in some but not all samples. Other…”