Low concentration of Tween-20 enhanced the adhesion and biofilm formation of Acidianus manzaensis YN-25 on chalcopyrite surface.

Although Tween-20 was used as an important catalyst to increase chalcopyrite bioleaching rate by acidophiles, the effect of Tween-20 on initial adhesion and biofilm development of acidophiles on chalcopyrite has not been explored until now. Herein, the role of Tween-20 in early attachment behaviors and biofilm development by Acidianus manzaensis strain YN-25 were investigated by adhesion experiments, adhesion force measurement, visualization of biofilm assays and a series of analyses including extended Derjaguin Landau Verwey Overbeek (DLVO) theory, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The bacterial adhesion experiments showed that 2 mg/L of Tween-20 increased the adhesion percentage (by 8%) of A. manzaensis YN-25. Tween-20 could promote the early adhesion of A. manzaensis YN-25 by changing the Lewis acid-base interaction and electrostatic force to increase total interaction energy and adhesion force. Besides, the functional groups on the surface of cells (carboxyl, hydroxyl and amino functional groups) contributed to the adhesion of A. manzaensis YN-25 on chalcopyrite. Furthermore, the promotion of biofilm formation by Tween-20 was mainly attributed to the reduction of S0 passivation layer formation and complexing more Fe3+ on chalcopyrite surface, contributing to the erosion of chalcopyrite and creating more corrosion pits. Live/dead staining showed low live/dead ratio (ranged from 0.35 to 1.32) during the biofilm development process. This report offers a better understanding of the effects of Tween-20 on attachment and biofilm development of acidophilic microorganisms and would lay a theoretical foundation for the better application of catalyst in bioleaching.

Ag+ significantly promoted the biofilm formation of thermoacidophilic archaeon Acidianus manzaensis YN-25 on chalcopyrite surface.

Silver ion (Ag+) is an important catalyst to improve chalcopyrite bio-dissolution, but its effects on initial adhesion behaviors and biofilm formation of acidophiles onto metal sulfide were still unknown. In this study, initial attachment behavior and adhesion force in the presence of Ag+ (0, 1, 2, 5, 10 and 20 mg/L) were comparatively analyzed for Acidianus manzaensis YN-25. Biofilm was observed by fluorescent images in the presence of 0, 1 and 2 mg/L Ag+. X-ray photoelectron spectroscopy (XPS) corroborated the catalytic mechanisms of Ag+ to biofilm formation. Results showed that Ag+ could significantly promote the attachment of cells on chalcopyrite, and the optimum concentration of Ag+ was 2 mg/L with the biggest percentage of attached cells (74%), followed by 5 mg/L (71%), whereas that for the control (0 mg/L) was only 61%. Ag+ significantly increased the interaction force between A. manzaensis YN-25 and chalcopyrite. Compared with the control, larger coverage of biofilm (up to 40% versus 32%) and more corrosion pits were observed on chalcopyrite in the presence of 2 mg/L Ag+. Moreover, Ag+ catalyzed chalcopyrite corrosion and accelerated biofilm formation by producing a loose porous Ag2S layer and Ag0 to decrease the resistivity. The live/dead ratio was small with a range of 0.31-1.38, suggesting that dead cells were a great slice during the whole life-cycle of biofilm on chalcopyrite. This report offers a profound insight into the promotion mechanism of Ag+ on adhesion behaviors and biofilm formation by thermoacidophilic archaeon under extremely acidic conditions.

Mechanism of Chronic Stress-induced Reduced Atherosclerotic Medial Area and Increased Plaque Instability in Rabbit Models of Chronic Stress.

BACKGROUND: Chronic stress contributes to increased risks of atherosclerotic diseases including heart disease, stroke, and transient ischemic attack. However, its underline mechanisms are poorly understood. This study aimed to elucidate the mechanism via which chronic stress exerts its effect on atherosclerosis (AS). METHODS: Fifty male New Zealand white rabbits were used. Aortic balloon-injury model was applied. Both social stress and physical stress methods were adopted to establish chronic stress models. The lumen stenotic degree, intimal and medial areas, maximum fibrous cap thickness, and plaque contents were measured with histological sections. Proteomic methods were applied to detect protein changes in abdominal aortas to identify the specialized mediators. Real-time reverse transcription-polymerase chain reaction was used for further verification and investigation. RESULTS: The stress rabbits exhibited lower body weight, worse fur state, more inactivity behavior, and higher serum cortisol level. Chronic stress was significantly associated with the decreased medial area and increased plaque instability, which was manifested by thinner fibrous caps, larger lipid cores, more macrophages, and new vessels but fewer smooth muscle cells and elastic fibers. After chronic stress, the apoptosis-related genes UBE2K, BAX, FAS, Caspase 3, Caspase 9, and P53 were upregulated, and BCL-2/BAX was down-regulated; the angiogenesis-related genes ANG and VEGF-A were also highly expressed in atherosclerotic arteries. CONCLUSIONS: Rabbit models of chronic stress were successfully established by applying both social stress and physical stress for 8 weeks. Chronic stress can reduce AS tunica media and accelerate plaque instability by promoting apoptosis and neovascularization.

Homologous HOmologous Black-Bright-blood and flexible Interleaved imaging sequence (HOBBI) for dynamic contrast-enhanced MRI of the vessel wall.

PURPOSE: To present a HOmologous Black-Bright-blood and flexible Interleaved imaging (HOBBI) sequence for dynamic contrast-enhanced magnetic resonance imaging (MRI) of the vessel wall. THEORY AND METHODS: A HOBBI sequence is proposed to acquire high-spatial-resolution black-blood and high-temporal-resolution bright-blood dynamic contrast-enhanced images in an interleaved fashion. Black-blood imaging allows for thin vessel wall evaluation, whereas bright-blood imaging obtains the arterial input function accurately. A simulation was performed to assess the accuracy of the pharmacokinetic parameters [transfer constant (K(trans) ) and fractional plasma volume (vp )] generated from HOBBI. In vivo evaluation was also used to validate HOBBI in an animal model of aortic atherosclerosis. RESULTS: In the simulation test, the estimated K(trans) and vp measured by HOBBI were more accurate than those from black-blood dynamic contrast-enhanced-MRI. In the animal model testing, K(trans) and vp also demonstrated good interscan reproducibility (K(trans) : ICC = 0.77, vp : ICC = 0.72, respectively). Additionally, K(trans) showed a significant increase from 1 month (0.026 ± 0.013 min(-1) ) to 2 months (0.069 ± 0.018 min(-1) ) in animal model plaque progression after balloon injury. CONCLUSION: The proposed HOBBI sequence was demonstrated to be feasible and accurate in estimating the pharmacokinetic parameters of the atherosclerotic vessel wall, and has potential to become an early screening tool for atherosclerosis disease.

Long-distance effects of insertional mutagenesis.

BACKGROUND: Most common systems of genetic engineering of mammalian cells are associated with insertional mutagenesis of the modified cells. Insertional mutagenesis is also a popular approach to generate random alterations for gene discovery projects. A better understanding of the interaction of the structural elements within an insertional mutagen and the ability of such elements to influence host genes at various distances away from the insertion site is a matter of considerable practical importance. METHODOLOGY/PRINCIPAL FINDINGS: We observed that, in the context of a lentiviral construct, a transcript, which is initiated at an internal CMV promoter/enhancer region and incorporates a splice donor site, is able to extend past a collinear viral LTR and trap exons of host genes, while the polyadenylation signal, which is naturally present in the LTR, is spliced out. Unexpectedly, when a vector, which utilizes this phenomenon, was used to produce mutants with elevated activity of NF-κB, we found mutants, which owed their phenotype to the effect of the insert on a gene located tens or even hundreds of kilobases away from the insertion site. This effect did not result from a CMV-driven transcript, but was sensitive to functional suppression of the insert. Interestingly, despite the long-distance effect, expression of loci most closely positioned to the insert appeared unaffected. CONCLUSIONS/SIGNIFICANCE: We concluded that a polyadenylation signal in a retroviral LTR, when occurring within an intron, is an inefficient barrier against the formation of a hybrid transcript, and that a vector containing a strong enhancer may selectively affect the function of genes far away from its insertion site. These phenomena have to be considered when experimental or therapeutic transduction is performed. In particular, the long-distance effects of insertional mutagenesis bring into question the relevance of the lists of disease-associated retroviral integration targets, which did not undergo functional validation.

Poly[tetraaquadi-mu3-malonato-calcium(II)zinc(II)].

The title complex, [CaZn(C3H2O4)2(H2O)4]n, is a two-dimensional polymer and consists of CaO8 and ZnO6 polyhedra linked together by malonate ligands. The Ca(II) cation, lying on a twofold axis, is coordinated by two water molecules and six malonate O atoms. The Zn(II) cation, which lies on an inversion center in an octahedral environment, is coordinated by four malonate O atoms in an equatorial arrangement and two water molecules in axial positions. The Zn-O and Ca-O bond lengths are in the ranges 2.0445 (12)-2.1346 (16) and 2.3831 (13)-2.6630 (13) angstroms, respectively. The structure comprises alternating layers along the [101] plane, the shortest Zn...Zn distance being 6.8172 (8) angstroms. The whole three-dimensional structure is maintained and stabilized by the presence of hydrogen bonds.