@article {3106, title = {Functional environmental proteomics: elucidating the role of a c-type cytochrome abundant during uranium bioremediation.}, journal = {ISME J}, volume = {10}, year = {2016}, month = {2016 Feb}, pages = {310-20}, abstract = {

Studies with pure cultures of dissimilatory metal-reducing microorganisms have demonstrated that outer-surface c-type cytochromes are important electron transfer agents for the reduction of metals, but previous environmental proteomic studies have typically not recovered cytochrome sequences from subsurface environments in which metal reduction is important. Gel-separation, heme-staining and mass spectrometry of proteins in groundwater from in situ uranium bioremediation experiments identified a putative c-type cytochrome, designated Geobacter subsurface c-type cytochrome A (GscA), encoded within the genome of strain M18, a Geobacter isolate previously recovered from the site. Homologs of GscA were identified in the genomes of other Geobacter isolates in the phylogenetic cluster known as subsurface clade 1, which predominates in a diversity of Fe(III)-reducing subsurface environments. Most of the gscA sequences recovered from groundwater genomic DNA clustered in a tight phylogenetic group closely related to strain M18. GscA was most abundant in groundwater samples in which Geobacter sp. predominated. Expression of gscA in a strain of Geobacter sulfurreducens that lacked the gene for the c-type cytochrome OmcS, thought to facilitate electron transfer from conductive pili to Fe(III) oxide, restored the capacity for Fe(III) oxide reduction. Atomic force microscopy provided evidence that GscA was associated with the pili. These results demonstrate that a c-type cytochrome with an apparent function similar to that of OmcS is abundant when Geobacter sp. are abundant in the subsurface, providing insight into the mechanisms for the growth of subsurface Geobacter sp. on Fe(III) oxide and suggesting an approach for functional analysis of other Geobacter proteins found in the subsurface.

}, keywords = {Amino Acid Sequence, Bacterial Proteins, Biodegradation, Environmental, Cytochrome c Group, Electron Transport, Ferric Compounds, Geobacter, Groundwater, Molecular Sequence Data, Oxidation-Reduction, Phylogeny, Proteomics, Sequence Alignment, Uranium}, issn = {1751-7370}, doi = {10.1038/ismej.2015.113}, author = {Yun, Jiae and Malvankar, Nikhil S and Ueki, Toshiyuki and Lovley, Derek R} } @article {3101, title = {Synthetic Biological Protein Nanowires with High Conductivity.}, journal = {Small}, volume = {12}, year = {2016}, month = {2016 Sep}, pages = {4481-5}, abstract = {

Genetic modification to add tryptophan to PilA, the monomer for the electrically conductive pili of Geobacter sulfurreducens, yields conductive protein filaments 2000-fold more conductive than the wild-type pili while cutting the diameter in half to 1.5 nm.

}, keywords = {Amino Acid Sequence, Electric Conductivity, Fimbriae, Bacterial, Geobacter, Nanowires, Proteins, Tryptophan}, issn = {1613-6829}, doi = {10.1002/smll.201601112}, author = {Tan, Yang and Adhikari, Ramesh Y and Malvankar, Nikhil S and Pi, Shuang and Ward, Joy E and Woodard, Trevor L and Nevin, Kelly P and Xia, Qiangfei and Tuominen, Mark T and Lovley, Derek R} } @article {3131, title = {A Geobacter sulfurreducens strain expressing pseudomonas aeruginosa type IV pili localizes OmcS on pili but is deficient in Fe(III) oxide reduction and current production.}, journal = {Appl Environ Microbiol}, volume = {80}, year = {2014}, month = {2014 Feb}, pages = {1219-24}, abstract = {

The conductive pili of Geobacter species play an important role in electron transfer to Fe(III) oxides, in long-range electron transport through current-producing biofilms, and in direct interspecies electron transfer. Although multiple lines of evidence have indicated that the pili of Geobacter sulfurreducens have a metal-like conductivity, independent of the presence of c-type cytochromes, this claim is still controversial. In order to further investigate this phenomenon, a strain of G. sulfurreducens, designated strain PA, was constructed in which the gene for the native PilA, the structural pilin protein, was replaced with the PilA gene of Pseudomonas aeruginosa PAO1. Strain PA expressed and properly assembled P. aeruginosa PilA subunits into pili and exhibited a profile of outer surface c-type cytochromes similar to that of a control strain expressing the G. sulfurreducens PilA. Surprisingly, the strain PA pili were decorated with the c-type cytochrome OmcS in a manner similar to the control strain. However, the strain PA pili were 14-fold less conductive than the pili of the control strain, and strain PA was severely impaired in Fe(III) oxide reduction and current production. These results demonstrate that the presence of OmcS on pili is not sufficient to confer conductivity to pili and suggest that there are unique structural features of the G. sulfurreducens PilA that are necessary for conductivity.

}, keywords = {Amino Acid Sequence, Cytochromes c, Electricity, Ferric Compounds, Fimbriae Proteins, Fimbriae, Bacterial, Geobacter, Methanosarcinaceae, Molecular Sequence Data, Oxidation-Reduction, Pseudomonas aeruginosa, Sequence Alignment}, issn = {1098-5336}, doi = {10.1128/AEM.02938-13}, author = {Liu, Xing and Tremblay, Pier-Luc and Malvankar, Nikhil S and Nevin, Kelly P and Lovley, Derek R and Vargas, Madeline} }