Biosorption of nickel(II) ions by using chemically pre-treated Sargassum filipendula biomass in a fixed bed column

The application of fixed bed adsorption is an important separation technique used for heavy metals in environmental pollution control. To design a fixed bed column, it is necessary to find dynamics data in the breakthrough curve form. The objective of this study was to model the biosorption process of nickel by using biomass of Sargassum filipendula in a fixed bed column. Experimental data were generated at 30°C, pH 3, flow rate of 6 ml/min and feed concentrations of 1, 1.5, 2, 3, 5 and 6 mequiv/l. Langmuir isotherm was used to represent the equilibrium data in the column (q _max = 2.496 mequiv/g, b = 0.456 l/mequiv) and in a batch operation of the system (q _max = 1.577 mequiv/g, b = 0.269 l/mequiv). These Langmuir parameters were used to simulate the continuous adsorption process of nickel. The partial differential equations model has taken into consideration the mass transfer resistance in the biosorbent as the key controlling phenomenon, which adequately represented the dynamic biosorption process of nickel.     

Valproic acid metabolites inhibit dihydrolipoyl dehydrogenase activity leading to impaired 2-oxoglutarate-driven oxidative phosphorylation

The effect of the antiepileptic drug valproic acid (VPA) on mitochondrial oxidative phosphorylation (OXPHOS) was investigated in vitro. Two experimental approaches were used, in the presence of selected respiratory-chain substrates: (1) formation of ATP in digitonin permeabilized rat hepatocytes and (2) measurement of the rate of oxygen consumption by polarography in rat liver mitochondria. VPA (0.1-1.0 mM) was found to inhibit oxygen consumption and ATP synthesis under state 3 conditions with glutamate and 2-oxoglutarate as respiratory substrates. No inhibitory effect on OXPHOS was observed when succinate (plus rotenone) was used as substrate. We tested the hypothesis that dihydrolipoyl dehydrogenase (DLDH) might be a direct target of VPA, especially its acyl-CoA intermediates. Valproyl-CoA (0.5-1.0 mM) and valproyl-dephosphoCoA (0.5-1.0 mM) both inhibited the DLDH activity, acting apparently by different mechanisms. The decreased activity of DLDH induced by VPA metabolites may, at least in part, account for the impaired rate of oxygen consumption and ATP synthesis in mitochondria if 2-oxoglutarate or glutamate were used as respiratory substrates, thus limiting the flux of these substrates through the citric acid cycle.     

Bacteriophage infection in rod-shaped gram-positive bacteria: evidence for a preferential polar route for phage SPP1 entry in Bacillus subtilis

Entry into the host bacterial cell is one of the least understood steps in the life cycle of bacteriophages. The different envelopes of Gram-negative and Gram-positive bacteria, with a fluid outer membrane and exposing a thick peptidoglycan wall to the environment respectively, impose distinct challenges for bacteriophage binding and (re)distribution on the bacterial surface. Here, infection of the Gram-positive rod-shaped bacterium Bacillus subtilis by bacteriophage SPP1 was monitored in space and time. We found that SPP1 reversible adsorption occurs preferentially at the cell poles. This initial binding facilitates irreversible adsorption to the SPP1 phage receptor protein YueB, which is encoded by a putative type VII secretion system gene cluster. YueB was found to concentrate at the cell poles and to display a punctate peripheral distribution along the sidewalls of B. subtilis cells. The kinetics of SPP1 DNA entry and replication were visualized during infection. Most of the infecting phages DNA entered and initiated replication near the cell poles. Altogether, our results reveal that the preferentially polar topology of SPP1 receptors on the surface of the host cell determines the site of phage DNA entry and subsequent replication, which occurs in discrete foci.