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

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.

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.

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.

Novel electrochemically active bacterium phylogenetically related to Arcobacter butzleri, isolated from a microbial fuel cell.

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 approximately 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.

Diversity and distribution of hemerythrin-like proteins in prokaryotes.

Hemerythrins are oxygen-binding proteins found in the body fluids and tissues of certain invertebrates. Oxygen is bound at a nonheme iron centre consisting of two oxo-bridged iron atoms bound to a characteristic set of conserved histidine: aspartate and glutamate residues with the motifs H-HxxxE-HxxxH-HxxxxD. It has recently been demonstrated biochemically that two bacterial proteins bearing the same motifs do in fact possess similar iron centres and bind oxygen in the same way. The recent profusion of prokaryotic genomic sequence data has shown that proteins bearing hemerythrin motifs are present in a wide variety of bacteria, and a few archaea. Some of these are short proteins as in eukaryotes; others appear to consist of a hemerythrin domain fused to another domain, generally a putative signal transduction domain such as a methyl-accepting chemotaxis protein, a histidine kinase, or a GGDEF protein (cyclic di-GMP synthase). If, as initial evidence suggests, these are in fact hemerythrin-like oxygen-binding proteins, then their diversity in prokaryotes far exceeds that seen in eukaryotes. Here, a survey is presented of prokaryotic protein sequences bearing hemerythrin-like motifs, for which the designation 'bacteriohemerythrins' is proposed, and their functions are speculated.

Physiological function and regulation of flavocytochrome c3, the soluble fumarate reductase from Shewanella putrefaciens NCIMB 400.

Shewanella putrefaciens produces a soluble flavocytochrome c under anaerobic growth conditions. This protein shares sequence similarity with the catalytic subunits of membrane-bound fumarate reductases from Escherichia coli and other bacteria and the purified protein has fumarate reductase activity. It is shown here that this enzyme, flavocytochrome c3, is essential for fumarate respiration in vivo since disruption of the chromosomal fccA gene, which encodes flavocytochrome c3, leads to a specific loss of the ability to grow with fumarate as terminal electron acceptor. Growth with nitrate, trimethylamine N-oxide (TMAO) and other acceptors was unaffected. The fccA gene is transcribed as a 2 kb monocistronic mRNA. An adjacent reading frame that bears limited sequence similarity to one of the membrane anchor subunits of E. coli fumarate reductase is not co-transcribed with fccA. Expression of the fccA gene is regulated by anaerobiosis and by the availability of alternative electron acceptors, particularly nitrate and TMAO. DNA sequences have been identified that are required for this regulation.