Real-time measurements of the redox states of c-type cytochromes in electroactive biofilms: a Confocal Resonance Raman Microscopy study

Virdis, Bernardino, Millo, Diego, Donose, Bogdan C. and Batstone, Damien J. (2014) Real-time measurements of the redox states of c-type cytochromes in electroactive biofilms: a Confocal Resonance Raman Microscopy study. PLoS One, 9 2: e89918.1-e89918.10. doi:10.1371/journal.pone.0089918


Author Virdis, Bernardino
Millo, Diego
Donose, Bogdan C.
Batstone, Damien J.
Title Real-time measurements of the redox states of c-type cytochromes in electroactive biofilms: a Confocal Resonance Raman Microscopy study
Journal name PLoS One   Check publisher's open access policy
ISSN 1932-6203
Publication date 2014-02-25
Year available 2014
Sub-type Article (original research)
DOI 10.1371/journal.pone.0089918
Open Access Status DOI
Volume 9
Issue 2
Start page e89918.1
End page e89918.10
Total pages 10
Place of publication San Francisco, CA, United States
Publisher Public Library of Science
Language eng
Abstract Confocal Resonance Raman Microscopy (CRRM) was used to probe variations of redox state of c-type cytochromes embedded in living mixed-culture electroactive biofilms exposed to different electrode polarizations, under potentiostatic and potentiodynamic conditions. In the absence of the metabolic substrate acetate, the redox state of cytochromes followed the application of reducing and oxidizing electrode potentials. Real-time monitoring of the redox state of cytochromes during cyclic voltammetry (CV) in a potential window where cytochromes reduction occurs, evidenced a measurable time delay between the oxidation of redox cofactors probed by CV at the electrode interface, and oxidation of distal cytochromes probed by CRRM. This delay was used to tentatively estimate the diffusivity of electrons through the biofilm. In the presence of acetate, the resonance Raman spectra of young (10 days, j = 208 +/- 49 mu A cm(-2)) and mature (57 days, j = 267 +/- 73 mu A cm(-2)) biofilms show that cytochromes remained oxidized homogeneously even at layers as far as 70 mu m from the electrode, implying the existence of slow metabolic kinetics that do not result in the formation of a redox gradient inside the biofilm during anode respiration. However, old biofilms (80 days, j = 190 +/- 37 mu A cm(-2)) with thickness above 100 mu m were characterized by reduced catalytic activity compared to the previous developing stages. The cytochromes in these biofilm were mainly in the reduced redox state, showing that only aged mixed-culture biofilms accumulate electrons during anode respiration. These results differ substantially from recent observations in pure Geobacter sulfurreducens electroactive biofilms, in which accumulation of reduced cytochromes is already observed in thinner biofilms, thus suggesting different bottlenecks in current production for mixed-culture and G. sulfurreducens biofilms.
Formatted abstract
Confocal Resonance Raman Microscopy (CRRM) was used to probe variations of redox state of c-type cytochromes embedded in living mixed-culture electroactive biofilms exposed to different electrode polarizations, under potentiostatic and potentiodynamic conditions. In the absence of the metabolic substrate acetate, the redox state of cytochromes followed the application of reducing and oxidizing electrode potentials. Real-time monitoring of the redox state of cytochromes during cyclic voltammetry (CV) in a potential window where cytochromes reduction occurs, evidenced a measurable time delay between the oxidation of redox cofactors probed by CV at the electrode interface, and oxidation of distal cytochromes probed by CRRM. This delay was used to tentatively estimate the diffusivity of electrons through the biofilm. In the presence of acetate, the resonance Raman spectra of young (10 days, j = 208±49 µA cm−2) and mature (57 days, j = 267±73 µA cm−2) biofilms show that cytochromes remained oxidized homogeneously even at layers as far as 70 µm from the electrode, implying the existence of slow metabolic kinetics that do not result in the formation of a redox gradient inside the biofilm during anode respiration. However, old biofilms (80 days, j = 190±37 µA cm−2) with thickness above 100 µm were characterized by reduced catalytic activity compared to the previous developing stages. The cytochromes in these biofilm were mainly in the reduced redox state, showing that only aged mixed-culture biofilms accumulate electrons during anode respiration. These results differ substantially from recent observations in pure Geobacter sulfurreducens electroactive biofilms, in which accumulation of reduced cytochromes is already observed in thinner biofilms, thus suggesting different bottlenecks in current production for mixed-culture and G. sulfurreducens biofilms.
Keyword Multidisciplinary Sciences
Science & Technology - Other Topics
MULTIDISCIPLINARY SCIENCES
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID 722.011.003
DP0985000
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2015 Collection
Advanced Water Management Centre Publications
 
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Created: Sat, 01 Mar 2014, 15:18:11 EST by Dr Bogdan Donose on behalf of Advanced Water Management Centre