High current density via direct electron transfer by the halophilic anode respiring bacterium Geoalkalibacter subterraneus

Abstract

In this study the characterization of Geoalkalibacter subterraneus is presented, a novel 11 halophilic anode respiring bacteria (ARB) previously selected and identified in a 12 potentiostically controlled bioelectrochemical system (BES) inoculated with sediments from a 13 salt plant. Pure culture electroactive biofilms of Glk. subterraneus were grown during 14 chronoamperometric batch experiments at a graphite electrode poised at +200 mV (vs. SCE) 15 with 10 mM acetate as electron donor. These biofilms exhibited the highest current density 16 (4.68 ± 0.54 A/m 2 ) reported on a planar material with a pure culture under saline conditions 17 (3.5% NaCl). To investigate possible anodic electron transfer (ET) mechanisms, cyclic 18 voltammetry (CV) of mature visible apparent reddish biofilms was performed under 19 bioelectrocatalytic substrate consumption (turnover) and in absence of substrate (non-20 turnover). CV evidenced a well defined typical sigmoidal shape and a pair of clear redox 21 couples under turnover and non-turnover conditions, respectively. Moreover, the calculation 22 of their formal potentials indicated the presence of a common ET mechanism present in both 23

Microbial characterization of anode-respiring bacteria within biofilms developed from cultures previously enriched in dissimilatory metal-reducing bacteria

“…The selection of Glk. subterraneus is not surprising since it is a well-known ARB (Carmona-Martínez et al, 2013;Miceli et al, 2012) and DMRB (Greene et al, 2009). This is in agreement with the expected effect of the DMRB-enrichment strategy.…”

Multi-system Nernst–Michaelis–Menten model applied to bioanodes formed from sewage sludge

“…(Bond et al, 2002), Geoalkalibacter sp. (Badalamenti et al, 2013;Carmona-Martinez et al, 2013). Phylogenetic identification using the ARB software revealed that the representative sequences of major OTUs belonging to this order were classified as Geobacteraceae related to Geobacter metallireducens (96% identity for the major OTUs of electrodes 1 and 3), a well-known electroactive bacterium (Bond et al, 2002) and as Desulfuromonadaceae related to Desulfuromonas michiganensis (93% identity for the third major OTU on electrode 2).…”

Bidirectional microbial electron transfer: Switching an acetate oxidizing biofilm to nitrate reducing conditions

“…In BES, the electron transfer between microorganisms and bioanodes has been well elucidated for a handful of anode-respiring bacteria (ARB) such as Geobacter sulfurreducens , Rhodopseudomonas palustris (Xing et al, 2008), Thermincola ferriacetica (Parameswaran et al, 2013), Geoalkalibacter subterraneus (Carmona-Martínez et al, 2013), and Shewanella oneidensis (Marsili et al, 2008). While bacteria within the Geobacteraceae are examples of ARB using DET to transport electrons from an available electron donor (organic matter) to the solid electrode (Carmona-Martínez et al, 2013;Fricke et al, 2008), members of the Shewanellaceae have been characterized for using both DET and MET (Carmona-Martinez et al, 2011;Marsili et al, 2008). However, the Shewanellaceae produce significantly less current densities.…”