In the bacterial periplasm, the reduction of nitrate to nitrite is catalysed by a periplasmic nitrate reductase (NAP) system, which is a species-dependent assembly of protein subunits encoded by the nap operon. The reduction of nitrate catalysed by NAP takes place in the 90 kDa NapA subunit, which contains a Mo-bis-molybdopterin guanine dinucleotide cofactor and one [4Fe"4S] iron-sulfur cluster. A review of the nap operons in the genomes of 19 strains of Shewanella shows that most genomes contain two nap operons. This is an unusual feature of this genus. The two NAP isoforms each comprise three isoform-specific subunits -NapA, a di-haem cytochrome NapB, and a maturation chaperone NapD -but have different membrane-intrinsic subunits, and have been named NAP-a (NapEDABC) and NAP-b (NapDAGHB). Sixteen Shewanella genomes encode both NAP-a and NAP-b. The genome of the vigorous denitrifier Shewanella denitrificans OS217 encodes only NAP-a and the genome of the respiratory nitrate ammonifier Shewanella oneidensis MR-1 encodes only NAP-b. This raises the possibility that NAP-a and NAP-b are associated with physiologically distinct processes in the environmentally adaptable genus Shewanella. IntroductionSpecies of the genus Shewanella are defined as pink-or salmon-coloured, Gram-negative, rod-shaped, facultative anaerobic bacteria with a single polar flagellum that are oxidase-and catalase-positive and can reduce trimethylamine N-oxide (TMAO) and nitrate (Venkateswaran et al., 1999). Almost all Shewanella species to date have been discovered in extreme aquatic or terrestrial environments, including deep-sea trench sediments, Antarctic ice cores, and sites contaminated with toxic compounds, including arsenic, remnants of military explosives or crude oil (Konstantinidis et al., 2009;Zhao et al., 2005Zhao et al., , 2006. Most Shewanella species are classifiable into one or more selected extremophilic subgroups: halophiles, psychrophiles or barophiles (Fredrickson et al., 2008;Hau & Gralnick, 2007;Pakchung et al., 2006). Most recently, Shewanella vesiculosa sp. nov. and Shewanella marina sp. nov. have been characterized from marine environments (Bozal et al., 2009;Park et al., 2009) and contribute to the 51 species of Shewanella identified at the time of writing (http://www.bacterio.cict.fr/). Some Shewanella species, most notably Shewanella oneidensis MR-1, can grow via the reduction of metal oxides -including Fe(III), Mn(IV), Cr(VI), U(VI), Tc(VI), V(V) -thiosulfate, elemental sulfur and arsenate (Burns & DiChristina, 2009;Carpentier et al., 2005;Konstantinidis et al., 2009;Malasarn et al., 2008;Murphy & Saltikov, 2007;Nealson & Saffarini, 1994;Nealson & Little, 1997). The respiratory versatility of Shewanella species has significant implications in bioremediation and in the assembly of microbial fuel cells (Fredrickson et al., 2008;Hou et al., 2009;Kim et al., 2002;Tiedje, 2002). Interest in the ecology and physiology of Shewanella at the genetic level is reflected by the 19 genome sequencing projects completed by the US ...

Impaired angiogenesis in ischemic tissue is a hallmark of diabetes. Thioredoxin-interacting protein (TXNIP) is an exquisitely glucose-sensitive gene that is overexpressed in diabetes. As TXNIP modulates the activity of the key angiogenic cytokine vascular endothelial growth factor (VEGF), we hypothesized that hyperglycemia-induced dysregulation of TXNIP may play a role in the pathogenesis of impaired angiogenesis in diabetes. In the current study, we report that high glucose–mediated overexpression of TXNIP induces a widespread impairment in endothelial cell (EC) function and survival by reducing VEGF production and sensitivity to VEGF action, findings that are rescued by silencing TXNIP with small interfering RNA. High glucose–induced EC dysfunction was recapitulated in normal glucose conditions by overexpressing either TXNIP or a TXNIP C247S mutant unable to bind thioredoxin, suggesting that TXNIP effects are largely independent of thioredoxin activity. In streptozotocin-induced diabetic mice, TXNIP knockdown to nondiabetic levels rescued diabetes-related impairment of angiogenesis, arteriogenesis, blood flow, and functional recovery in an ischemic hindlimb. These findings were associated with in vivo restoration of VEGF production to nondiabetic levels. These data implicate a critical role for TXNIP in diabetes-related impairment of ischemia-mediated angiogenesis and identify TXNIP as a potential therapeutic target for the vascular complications of diabetes.

Environmental Context.Since the discovery of a diverse array of microbial life associated with hydrothermal vents on the ocean floor, where conditions are hot, reducing and acidic, scientists have been seeking insight into the mechanisms used by ‘extremophilic’ organisms (those that reside permanently under environmental extremes of temperature (hot or cold), pH (acid or alkaline), salinity, or pressure) to thrive under such seemingly inhospitable conditions. Abstract.The discovery of an abundance of microorganisms that flourish in a diverse range of environments, from the frigid waters of the Antarctic, to the superheated waters of the hydrothermal vents, at the bottom of 11-km deep ocean trenches and in salt-saturated lakes, has fuelled research aimed to understand the novel survival strategies evolved by these extreme-loving (extremophilic) organisms. Adaptations of biomolecules (proteins, nucleic acids, membranes and small molecules) evolved by extremophiles are wide ranging. Compared with a protein from a ‘regular’ organism, the extremophilic analogue might feature changes to the relative frequencies of amino acid residues that modulate the properties (e.g. conformational flexibility and stability) of the protein under conditions of the specific environmental challenge. The integrity of RNA and DNA from extremophiles may be maintained by subtle structural changes to RNA nucleobases and, in the case of (hyper)thermophiles, the expression of the enzyme reverse gyrase, which catalyses positive DNA supercoiling. The expression of small molecular weight heat-shock or related caretaker proteins also features as a common adaptive strategy for maintaining cell viability at environmental extremes. Membrane architecture in extremophiles can be modulated by the environmental temperature, with additional thermal stability in membranes from some hyperthermophiles conferred by novel (cyclised) lipid chains. In addition, a selection of osmolytes and small molecules are biosynthesised or sequestered by extremophilic organisms that have adapted to conditions of high salt and/or micronutrient deprivation.

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There is a progressive impairment of vascular repair mechanisms with advancing age concomitant with a steady decline in circulating androgen levels in men. Emerging evidence indicates androgens regulate angiogenesis; however, little research has focused on the impact of age upon androgen-mediated regulation of angiogenic mechanisms. Human dermal fibroblasts from young (<30 years) and older (>65 years) men were incubated with DHT, with or without androgen receptor antagonist hydroxyflutamide, or phosphoinositide 3-kinase inhibitor. Fibroblast-conditioned medium was used to stimulate angiogenic functions in human umbilical vein endothelial cells. Nuclear fractionation and fluorescence microscopy were used to study androgen receptor (AR) distribution. Conditioned medium from fibroblasts of young men, but not old men, treated with DHT produced a 3-fold increase in human umbilical vein endothelial cell tubulogenesis and 2-fold increase in migration via increased vascular endothelial growth factor (VEGF) expression and secretion, predominantly of VEGF145. DHT-induced VEGF secretion from fibroblasts of young men was AR-dependent and increased AKT phosphorylation, which was abrogated by phosphoinositide 3-kinase inhibition. By contrast, fibroblasts from older men were unresponsive to DHT and lacked androgen-mediated enhancement in VEGF production. These findings were associated with reduced AR nuclear translocation in old fibroblasts. The failure of DHT-induced paracrine stimulation of angiogenesis in fibroblasts from older men is likely due to defective nuclear translocation of AR. This first demonstration of androgen resistance (or insensitivity) acquired by human fibroblasts with aging suggests that pharmacological testosterone therapy for old men may be less effective in enhancing angiogenesis and facilitating tissue regeneration mechanisms reliant on paracrine release of VEGF.