Electrochemical characterization of Geobacter sulfurreducens cells immobilized on graphite paper electrodes

Bacteria able to transfer electrons to conductive surfaces are of interest as catalysts in microbial fuel cells, as well as in bioprocessing, bioremediation, and corrosion. New procedures for immobilization of Geobacter sulfurreducens on graphite electrodes are described that allow routine, repeatable electrochemical analysis of cell-electrode interactions. Immediately after immobilizing G. sulfurreducens on electrodes, electrical current was obtained without addition of exogenous electron shuttles or electroactive polymers. Voltammetry and impedance analysis of pectin-immobilized bacteria transferring electrons to electrode surfaces could also be performed. Cyclic voltammetry of immobilized cells revealed voltage-dependent catalytic current similar to what is commonly observed with adsorbed enzymes, with catalytic waves centered at -0.15 V (vs. SHE). Electrodes maintained at +0.25 V (vs. SHE) initially produced 0.52 A/m(2) in the presence of acetate as the electron donor. Electrical Impedance Spectroscopy of coatings was also consistent with a catalytic mechanism, controlled by charge transfer rate. When electrodes were maintained at an oxidizing potential for 24 h, electron transfer to electrodes increased to 1.75 A/m(2). These observations of electron transfer by pectin-entrapped G. sulfurreducens appear to reflect native mechanisms used for respiration. The ability of washed G. sulfurreducens cells to immediately produce electrical current was consistent with the external surface of this bacterium possessing a pathway linking oxidative metabolism to extracellular electron transfer. This electrochemical activity of pectin-immobilized bacteria illustrates a strategy for preparation of catalytic electrodes and study of Geobacter under defined conditions.     

Chemical modification of alpha-chymotrypsin for obtaining high transesterification activity in low water organic media

Alpha-chymotrypsin was made more hydrophilic by modifying 11 (out of 16) ε-amino groups with pyromellitic dianhydride. The hydrophilic preparation was precipitated with n-propanol. This preparation gave significantly higher initial rates at the optimum a_w (127.51 nmol mg^?1 min^?1 in n-octane and 21.30 nmol mg^?1 min^?1 in acetonitrile at a_w=0.33) compared with the lyophilized preparation (53.50 nmol mg^?1 min^?1 in n-octane and 0.26 nmol mg^?1 min^?1 in acetonitrile at a_w=0.97). FT-IR showed that the precipitate of modified alpha-chymotrypsin has a higher content of alpha-helices and beta-sheets compared to the lyophilized powder.     

In vitro propagation,clonal fidelity and phytochemical analysis of <Emphasis Type="Italic">Rhodiola imbricata</Emphasis> Edgew: a rare trans-Himalayan medicinal plant

The present study focuses on development of a micropropagation protocol for true to type plants of Rhodiola imbricata, an endangered medicinal plant found in trans-Himalayan Leh-Ladakh region of India. It also aims at analyzing the pharmaceutically important secondary metabolites and antioxidant potential of in vitro and in vivo plants. Various cytokinins and auxins were tested for shoot proliferation and in vitro rooting of the microshoots, respectively. Random primers were used for checking genetic uniformity at different stages of micropropagation. Pharmaceutically important secondary metabolites of R. imbricata such as Rosavin, total polyphenols and free radical scavenging activity were analyzed by HPLC. Among different cytokinins used, BAP (5 µM) and TDZ (1 µM) were found to perform better in terms of shoot proliferation, shoot length and number of leaves as compared to other concentrations. For rooting of microshoots, a lower concentration of NAA (0.5 µM) yielded more efficient rooting of micro shoots (17.33 roots per micro shoot). In vitro rooted microshoots were hardened and showed 60% survival rate. The content of gallic acid, chlorogenic acid and 4-hydroxybenzoic acid was higher in the in vivo plant. The amount of ferulic acid was higher in the in vitro raised plant when compared to field grown plant. Furthermore, caffeic acid and p-coumaric acid were higher in the in vitro raised plants as compared to field grown plants. This work will facilitate in conservation of this endangered herb and provide necessary plant materials for various biotechnological and pharmaceutical applications.     

Complexation and detoxification of Zn and Cd in metal accumulating plants

Metal accumulating plants exposed to toxic levels of zinc (Zn) and cadmium (Cd) uptake metals through extracellular and intracellular complexation with inorganic and organic ligand formation. However, little is known about the nature and formation mechanism of these metal–ligand complexes. Though, Zn and Cd have many similar chemical properties, yet their complexation and compartmentalization in plants vary with plant species. In principal, the question arises what factors govern Zn and Cd partitioning in plants? What form of the metal is taken up by the root, and is further distributed and accumulated in both vegetative and reproductive tissues? Therefore, the aim of present study is to address several questions concerning the mechanisms of Zn and Cd coordination and compartmentalization in plants using X-ray absorption spectroscopy (XAS) technique. XAS allows direct determination of elemental oxidation states and coordination environments in different plant tissues. This review article briefly explains some other important techniques of XAS; EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure), which are employed for determining Zn and Cd complexation within the plant. Therefore, In present review, the predominant as well as the minor chemical forms of Zn and Cd present in particular plant tissue have been discussed which could give better insight towards metal accumulation and detoxification mechanisms operated in plants. This information could assist in employing suitable hyperaccumulator plants for metal phytoextraction and reclamation of metal contaminated sites.     

Antidiabetic, antihypercholesterolaemic and antioxidant effect of Ocimum sanctum (Linn) seed oil

Antihyperlipidaemic and antioxidant effect of Ocimum sanctum Linn. seed oil (OSSO) was investigated in rabbits. Administration of OSSO (0.8 g/kg body weight/day) for four weeks, in cholesterol (100 mg/kg body weight/day) fed rabbits significantly decreased serum cholesterol, triacylglycerol and LDL-+VLDL-cholesterol as compared to untreated cholesterol fed group. There was significant fall in atherogenic index in OSSO treated group. In addition, treatment with OSSO decreased lipid peroxidation and increased reduced glutathione content in blood. Antidiabetic effect of O. sanctum seed oil was evaluated in alloxan diabetic rabbits. Two weeks treatment of diabetic rabbits with OSSO (0.8 gm/kg/day) showed no significant hypoglycaemic effect. Results of the present study show that OSSO has hypocholesterolaemic and antioxidant effects but it does not have antidiabetic effect.     

Mitochondrial E3 ubiquitin ligase MARCH5 controls mitochondrial fission and cell sensitivity to stress-induced apoptosis through regulation of MiD49 protein

Ubiquitin- and proteasome-dependent outer mitochondrial membrane (OMM)-associated degradation (OMMAD) is critical for mitochondrial and cellular homeostasis. However, the scope and molecular mechanisms of the OMMAD pathways are still not well understood. We report that the OMM-associated E3 ubiquitin ligase MARCH5 controls dynamin-related protein 1 (Drp1)-dependent mitochondrial fission and cell sensitivity to stress-induced apoptosis. MARCH5 knockout selectively inhibited ubiquitination and proteasomal degradation of MiD49, a mitochondrial receptor of Drp1, and consequently led to mitochondrial fragmentation. Mitochondrial fragmentation in MARCH5^−/− cells was not associated with inhibition of mitochondrial fusion or bioenergetic defects, supporting the possibility that MARCH5 is a negative regulator of mitochondrial fission. Both MARCH5 re-expression and MiD49 knockout in MARCH5^−/− cells reversed mitochondrial fragmentation and reduced sensitivity to stress-induced apoptosis. These findings and data showing MARCH5-dependent degradation of MiD49 upon stress support the possibility that MARCH5 regulation of MiD49 is a novel mechanism controlling mitochondrial fission and, consequently, the cellular response to stress.     

Defining the pathway of worm-like amyloid fibril formation by the mouse prion protein by delineation of the productive and unproductive oligomerization reactions

Aggregation reactions of proteins leading to amyloid fibril formation are often characterized by early transient accumulation of a heterogeneous population of soluble oligomers differing in size and structure. Delineating the kinetic roles of the different oligomeric forms in fibril formation has been a major challenge. The aggregation of the mouse prion protein to form worm-like amyloid fibrils at low pH is known to proceed via a β-rich oligomer ensemble, which is shown here to be comprised of two subpopulations of oligomers that differ in size and internal structure. The relative populations of the two oligomers can be tuned by varying the concentration of NaCl present. By demonstrating that the apparent rate constant for the formation of fibrils is dependent linearly on the concentration of the larger oligomer and is independent of the concentration of the smaller oligomer, we show that the larger oligomer is a productive intermediate that accumulates on the direct pathway of aggregation from monomer to worm-like fibrils. The smaller oligomer is shown to be populated off the pathway of the larger oligomer and, hence, is not directly productive for fibril formation. The relative populations of the two oligomers can also be tuned by single-amino acid residue changes in the sequence of the protein. The different protein variants yield worm-like fibrils of different lengths, and the apparent rate of formation of the fibrils by the mutant variants is also shown to be dependent on the concentration of the larger but not of the smaller oligomer formed.     

Complete Genome Sequence of Phytopathogenic Pectobacterium carotovorum subsp. carotovorum Bacteriophage PP1

Pectobacterium carotovorum subsp. carotovorum is a phytopathogen causing soft rot disease on diverse plant species. To control this plant pathogen, P. carotovorum subsp. carotovorum-targeting bacteriophage PP1 was isolated and its genome was completely sequenced to develop a novel biocontrol agent. Interestingly, the 44,400-bp genome sequence does not encode any gene involved in the formation of lysogen, suggesting that this phage may be very useful as a biocontrol agent because it does not make lysogen after host infection. This is the first report on the complete genome sequence of the P. carotovorum subsp. carotovorum-targeting bacteriophage, and it will enhance our understanding of the interaction between phytopathogens and their targeting bacteriophages.