Autori: Bernardino Virdis , Falk Harnisch , Damien J. Batstone , Korneel Rabaey and Bogdan C. Donose
Editorial: Energy & Environmental Science, 5, p.7017-7024, 2012.
Electrochemically active biofilms rely on microorganisms capable of extracellular electron transfer.
Such biofilms are involved in the dissimilatory reduction of metal oxides in natural environments as
well as electricity driving and driven processes at the electrodes of microbial bioelectrochemical
systems. In this work we present the application of confocal Raman microscopy (CRM) as a noninvasive,
label-free, and in vivo characterization method of acetate oxidizing anodic biofilms, grown
from primary wastewater inoculum and dominated by Geobacter species (>85% of sequences analysed
using pyrotag sequencing). Using the resonance Raman effect of the heme protein cytochrome c (Cyt
c)—an ubiquitous component of extracellular electron transfer reactions—it was possible to collect
characteristic spectral information of electrochemically active biofilms at pixel integration times of 0.2 s
and an excitation wavelength of 532 nm. This allowed monitoring of biofilm development at different
growth stages, without impacting its structural or metabolic activity. Furthermore, we demonstrate the
possibility of non-invasive investigation of the spatial redox electrochemistry (up to a compositional
level) of electrochemically active biofilms, as we observed significant changes in the vibrational
properties of Cyt c resulting from shifts in the anodic potential between different redox conditions.
Compared to conventional methods requiring destructive sample manipulation and fixation, the
proposed approach based on CRM allows the non-invasive analysis of microbial aggregates with
minimal sample preparation or prior knowledge of the sample.
Cuvinte cheie: electrochemically active biofilms, Raman microscopy