Highly conductive textile electrodes for microbial fuel cells

High performance microbial fuel cells (MFCs) require effective mech. and elec. interaction between electrode surfaces and attached microbial biofilms. Three-dimensional porous electrodes with large-surface area offer an attractive means of achieving this objective. Here we report a novel porous electrode in which a conductive carbon nanotube (CNT) coating is applied to a com. textile. The CNT-textile composite was evaluated as an anode in a MFC. The macroporous structure of textile allowed growth of biofilm inside the anode, increasing the active surface area for electron transfer. The CNT-textile composite outperformed a normal carbon cloth electrode, and appears promising for MFC applications

Supplementary Material for: Pseudomonas stutzeri KC carries the pdt genes for carbon tetrachloride degradation on an integrative and conjugative element

Pseudomonas stutzeri KC can rapidly degrade carbon tetrachloride (CCl4) to CO2 by a fortuitous reaction with pyridine-2,6-bis(thiocarboxylic acid), a metal chelator encoded by pdt genes. These genes were first identified after a spontaneous mutant, strain CTN1, lost the ability to degrade CCl4. Here we report the complete genome of strain KC and show that these pdt genes are located on an integrative and conjugative element (ICE), designated ICEPsstKC. Comparative genome analyses revealed homologues of pdt genes in genomes of members of other gammaproteobacterial orders. Discrepancies between the tree topologies of the deduced pdt gene products and the host phylogeny based on 16S rRNA provided evidence for horizontal gene transfer (HGT) in several sequenced strains of these orders. In addition to ICEPsstKC, HGT may be have been facilitated by other mobile genetic elements, as indicated by the location of the pdt gene cluster adjacent to fragments of other ICEs and prophages in several genome assemblies. We could here show that the majority of cells from the culture collection DSMZ had lost the ICE. The presence of the pdt gene cluster on mobile genetic elements has important implications for the bioremediation of CCl4 for bioremediation of CCl4 and needs consideration when selecting suitable strains

Application of high-density oligonucleotide microarrays to the study of Crenarchaeota community structure and dynamics in an aerated activated sludge wastewater treatment plant

Despite the fact that biological wastewater treatment is practiced widely to remove organics, nutrients, toxics, and pathogens from polluted water, little is known about the ecology of microbial communities in bioreactors. In particular, the prevalence, diversity, functional inlpo11ance, and population dynamics of nonthermophilic Crenarchaeota in aerated activated sludge wastewater treatment systems remain virtually unknown. The aim of this study was to elucidate the diversity and dynamics of nonthermophilic Crenarchaeota in aerated activated sludge systems and to link these dynamics to operational or environmental parameters. To this end, we used high-density 16S rDNA phylogenetic microarrays containing 500,000 probes to monitor bacterial and archaeal population dynamics in monthly samples from the aeration basin of a local municipal activated sludge wastewater treatnlent plant (WWTP) for a period of one year. Operational data were collected concurrently. Our results revealed a highly diverse prokaryotic community in the WWTP, with an average of 1606 bacterial and archaeal phylotypes detected at each sampling point. Eleven distinct and highly dynamic nonthermophilic Crenarchaeota phylotypes from groups l.la and l.lb were detected in 11 of the 12 months examined. Within each Crenarchaeal phylotype, 16S rRNA gene copy number varied by nearly an order of magnitude dUling the study period. Seven main covarying archaeal response groups in this time period were identified based on hierarchical clustering. The majority of the identified nonthermophilic Crenarchaeota phylotypes fell within the same response group, indicating significant covariation in population size among these phylotypes during the year of sampling. Our results suggest that nonthermophilic Crenarchaeota may play a previously unrecognized role in aerated activated sludge bioreactors. To our knowledge, this is the first application of high-density phylogenetic DNA microarray methods to the analysis of microbial community structure in activated sludge bioreactors

Microarray-Based Analysis of Microbial Community Composition and Dynamics in Uranium Bioremediation

A field-scale system is being used for evaluating in situ biological reduction and immobilization of U(VI) in the DOE ERSP Field Research Center, Oak Ridge, TN. Above-ground treatment of groundwater, including nitrate removal pre-conditions the groundwater for subsurface uranium immobilization. Treated water was then injected into the subsurface with ethanol to stimulate microbial reduction of U(VI) to insoluble U(IV). The microbial community dynamics from one of the 4 frequently sampled monitoring wells (FW 102-3) was intensively analyzed with a functional gene array containing >24,000 probes and covering 10,000 genes in 150 gene categories. The results indicated that during the uranium reduction period, both FeRB and SRB populations reached their highest levels at Day 212, followed by a gradual decrease over 500 days. The uranium concentrations in the groundwater were significantly correlated with the total abundance of c-type cytochrome genes (r=0.73, p<0.05) from Geobacter-type FeRB and Desulfovibrio-type SRB, and with the total abundance of dsrAB (dissimilatory sulfite reductase) genes (r=0.88, p<0.05). The Mantel test of microarray and chemical data also indicated that there was significant correlation between the differences of uranium concentrations and those of total c-cytochrome gene abundance (r=0.75, p <0.001) or dsrAB gene abundance (r=0.72, p<0.01). The changes of more than dozen of individual c-type cytochrome genes from Geobacter sulfurreducens and Desulfovibrio desulfuricans showed significant correlations to the changes of uranium concentrations among different time points. Also the changes of more than 10 dsrAB-containing populations, including both cultured (e.g. D. desulfuricans, D. termitidis, Desulfotomaculum kuznetsovii,) and non-cultured SRB were significantly related to the changes in uranium concentrations, indicating their importance in uranium reduction. Interestingly, as expected, the changes of several dsrAB-containing sulfate-reducing populations previously recovered from this site showed significant correlations to the differences of uranium concentrations