Microbial Communities Associated with Electrodes Harvesting Electricity from a Variety of Aquatic Sediments

Abstract

The microbial communities associated with electrodes from underwater fuel cells harvesting electricity from five different aquatic sediments were investigated. Three fuel cells were constructed with marine, salt-marsh, or freshwater sediments incubated in the laboratory. Fuel cells were also deployed in the field in salt marsh sediments in New Jersey and estuarine sediments in Oregon, USA. All of the sediments produced comparable amounts of power. Analysis of 16S rRNA gene sequences after 3-7 months of incubation demonstrated that all of the energy-harvesting anodes were highly enriched in microorganisms in the delta-Proteobacteria when compared with control electrodes not connected to a cathode. Geobacteraceae accounted for the majority of delta-Proteobacterial sequences or all of the energy-harvesting anodes, except the one deployed at the Oregon estuarine site. Quantitative PCR analysis of 16S rRNA genes and culturing studies indicated that Geobacteraceae were 100-fold more abundant on the marine-deployed anodes versus controls. Sequences most similar to microorganisms in the family Desulfobulbaceae predominated on the anode deployed in the estuarine sediments, and a significant proportion of the sequences recovered from the freshwater anodes were closely related to the Fe(III)-reducing isolate, Geothrix fermentans. There was also a specific enrichment of microorganisms on energy harvesting cathodes, but the enriched populations varied with the sediment/water source. Thus, future studies designed to help optimize the harvesting of electricity from aquatic sediments or waste organic matter should focus on the electrode interactions of these microorganisms which are most competitive in colonizing anodes and cathodes.

Comparison of 16S rRNA, nifD, recA, gyrB, rpoB and fusA genes within the family Geobacteraceae fam. nov.

“…'Geopsychrobacter electrodophilus' A2, 'Geopsychrobacter multivorans' A1 and Desulfuromusa sp. strain S1 were isolated from the surface of a current-harvesting electrode in a marine fuel cell (Holmes et al, 2004). Geobacter hydrogenophilus DSM 13691 T and Geobacter chapellei DSM 13688 T were obtained from the laboratory of John Coates.…”

“…Desulfuromusa sp. strain S1, 'Geopsychrobacter electrodophilus' A2 and 'Geopsychrobacter multivorans' A1 were grown at 20 uC in APW medium (Coates et al, 1995) with Fe(III) oxide (60 mM) or colloidal S 0 (10 mM) as electron acceptor and acetate (5 mM) as electron donor (Holmes et al, 2004). Malonomonas rubra was grown in APW medium (Coates et al, 1995) with 40 mM fumarate, 40 % of the recommended amount of MgCl 2 .6H 2 O and CaCl 2 .2H 2 O and 0?36 g NaS.9H 2 O l 21 as reductant.…”

“…Furthermore, the finding that geobacteraceae can account for about 40-90 % of the total microbial community under Fe(III)-reducing conditions in some subsurface environments (Anderson et al, 2003;Holmes et al, 2002) suggests that subsurface Fe(III)-reducing communities may provide the type of low-diversity community that is most amenable to environmental genomics studies. This is also true for the surface of electrodes harvesting energy from aquatic sediments, in which geobacteraceae typically comprise about half of the microbial community Holmes et al, 2004;Tender et al, 2002).…”

Flux Analysis of Central Metabolic Pathways in Geobacter metallireducens during Reduction of Soluble Fe(III)-Nitrilotriacetic Acid

“…Detailed studies of their metabolism have revealed them to be capable of bioremediation of several heavy metals, including uranium, plutonium, technetium, and vanadium, as well as biodegradation of several organic contaminants, including monoaromatic hydrocarbons (16,17,26). More recently, Geobacter species have been used to generate electricity from waste organic matter (2,15,19). These unique metabolisms make Geobacter species important players in the contaminated subsurface environment (18).…”

Thin film nanoporous electrodes for the selective catalysis of oxygen in abiotically catalysed micro glucose fuel cells

“…These have often occupied more than half the volume of the implantable device [9] and consequently alternative means of power sources that may offer higher energy densities or lifetimes have been considered. Energy harvesters based on vibration [10,11], thermal gradients [12,13] and exogeneous chemicals [14,15] have therefore emerged as the most promising candidates. In this respect, the use of glucose and dissolved oxygen (DO) may hold the best promise of a long term energy supply for electronic implants due to their relative abundance in all tissues and their limited-dependency to ambient factors.…”