F. Bruce Ward

Novel Electrochemically Active Bacterium Phylogenetically Related to Arcobacter butzleri, Isolated from a Microbial Fuel Cell

ABSTRACT Exoelectrogenic bacteria are organisms that can transfer electrons to extracellular insoluble electron acceptors and have the potential to be used in devices such as microbial fuel cells (MFCs). Currently, exoelectrogens have been identified in the Alpha-, Beta-, Gamma- and Deltaproteobacteria, as well as in the Firmicutes and Acidobacteria. Here, we describe use of culture-independent methods to identify two members of the genus Arcobacter in the Epsilonproteobacteria that are selectively enriched in an acetate-fed MFC. One of these organisms, Arcobacter butzleri strain ED-1, associates with the electrode and rapidly generates a strong electronegative potential as a pure culture when it is supplied with acetate. A mixed-community MFC in which ∼90% of the population is comprised of the two Arcobacter species generates a maximal power density of 296 mW/liter. This demonstration of exoelectrogenesis by strain ED-1 is the first time that this property has been shown for members of this genus.

Predicted structure and possible ionmotive mechanism of the sodium-linked NADH-ubiquinone oxidoreductase of Vibrio alginolyticus.

Two groups have now published sequences of the six genes contained in the operon coding for the sodium‐linked NADH‐ubiquinone oxidoreductase of Vibrio alginolyticus. Sequence analyses indicate that this enzyme is unrelated to other known respiratory NADH dehydrogenases. A search for cofactor motifs suggests that the enzyme contains only one FAD, a ferredoxin‐type iron sulphur centre, and the NADH‐binding site. These are all located on NqrF, a subunit that can be recognized as a new member of a large diverse family of NAD(P)H‐oxidizing flavoenzymes. A possible model of ion‐coupling is presented, based upon this new information.

Complete genome sequences of Arcobacter butzleri ED-1 and Arcobacter sp. strain L, both isolated from a microbial fuel cell.

Arcobacter butzleri strain ED-1 is an exoelectrogenic epsilonproteobacterium isolated from the anode biofilm of a microbial fuel cell. Arcobacter sp. strain L dominates the liquid phase of the same fuel cell. Here we report the finished and annotated genome sequences of these organisms.

A multipurpose modular system for high-resolution microscopy at high hydrostatic pressure.

We have developed a modular system for high-resolution microscopy at high hydrostatic pressure. The system consists of a pressurized cell of volume approximately 100 microl, a temperature controlled holder, a ram, and a piston. We have made each of these components in several versions which can be interchanged to allow a wide range of applications. Here, we report two pressure cells with pressure ranges 0.1-700 MPa and 0.1-100 MPa, which can be combined with hollow or solid rams and pistons. Our system is designed to work with fluorescent samples (using a confocal or epifluorescence microscope), but also allows for transmitted light microscopy via the hollow ram and piston. The system allows precise control of pressure and temperature (-20 to 70 degrees C), as well as rapid pressure quenching. We demonstrate its performance and versatility with two applications: time-resolved imaging of colloidal phase transitions caused by pressure changes between 0.1 and 100 MPa, and imaging the growth of Escherichia coli bacteria at 50 MPa. We also show that the isotropic-nematic phase transition of pentyl-cyanobiphenyl (5CB) liquid crystal provides a simple, convenient, and accurate method for calibrating pressure in the range 0.1-200 MPa.

Genes Required for Growth at High Hydrostatic Pressure in Escherichia coli K-12 Identified by Genome-Wide Screening

Despite the fact that much of the global microbial biosphere is believed to exist in high pressure environments, the effects of hydrostatic pressure on microbial physiology remain poorly understood. We use a genome-wide screening approach, combined with a novel high-throughput high-pressure cell culture method, to investigate the effects of hydrostatic pressure on microbial physiology in vivo. The Keio collection of single-gene deletion mutants in Escherichia coli K-12 was screened for growth at a range of pressures from 0.1 MPa to 60 MPa. This led to the identification of 6 genes, rodZ, holC, priA, dnaT, dedD and tatC, whose products were required for growth at 30 MPa and a further 3 genes, tolB, rffT and iscS, whose products were required for growth at 40 MPa. Our results support the view that the effects of pressure on cell physiology are pleiotropic, with DNA replication, cell division, the cytoskeleton and cell envelope physiology all being potential failure points for cell physiology during growth at elevated pressure.

Single-molecule imaging at high hydrostatic pressure

Direct microscopic fluorescence imaging of single molecules can provide a wealth of mechanistic information, but up to now, it has not been possible under high pressure conditions, due to limitations in microscope pressure cell design. We describe a pressure cell window design that makes it possible to image directly single molecules at high hydrostatic pressure. We demonstrate our design by imaging single molecules of Alexa Fluor 647 dye bound to DNA, at 120 and 210 bar, and following their fluorescence photodynamics. We further show that the failure pressure of this type of pressure cell window can be in excess of 1 kbar.

Draft Genome Sequence of Magnetovibrio blakemorei Strain MV-1, a Marine Vibrioid Magnetotactic Bacterium

ABSTRACT We report here the genome sequence of Magnetovibrio blakemorei MV-1, a marine vibrioid magnetotactic bacterium with a single polar flagellum. The current assembly consists of 91 contigs with a combined size of 3,638,804 bp (54.3% G+C content). This genome allows for further investigations of the molecular biomineralization mechanisms of magnetosome formation.