Phosphate uptake kinetics and its regulation in N2- fixing cyanobacterium Anabaena oryzae Fritsch under salt stress

Phosphorous (P) starved cells of the cyanobacterium Anabaena oryzae showed higher phosphate uptake rates than P-sufficient cells. The P-uptake obeyed saturation kinetics. The Km value for Pdeficientcells was lower (54.34 mM) than P-sufficient cells (82.64 mM) while Vmax was higher in Pdeficient and lower in P-sufficient cells. Salinity (NaCl) stimulated phosphate uptake significantly in thecyanobacterium which is followed by greater amount of P-accumulation in the form of polyphosphate bodies. Inhibition of P-uptake in P-deficient cells was 45% in dark grown compared to light grown cells.P-uptake was inhibited 52 and 85% in culture treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU; 10 mM) and carbonyl cyanide m-chloro phenylhydrazone (CCCP; 100 mM), respectively,suggesting that energy for uptake could be derived from oxidative phosphorylation and photophosphorelation

Exploring the possibility of enhancing the figure-of-merit ( >> 2) of Na0.74_{0.74}CoO2_{2}: A combined experimental and theoretical study

Search of new thermoelectric (TE) materials with high \textit{figure-of-merit} (ZT) is always inspired the researcher in TE field. Here, we present a combined experimental and theoretical study of TE properties of Na$_{0.74}$CoO$_{2}$ compound in high-temperature region. The experimental Seebeck coefficient (S) is found to vary from 64 to 118 $\mu$V/K in the temperature range $300-620$ K. The positive values of S are indicating the dominating p-type behaviour of the compound. The observed value of thermal conductivity ($\kappa$) is $\sim$ 2.2 W/m-K at 300 K. In the temperature region $300-430$ K, the value of $\kappa$ increases up to $\sim$ 2.6 W/m-K and then decreases slowly till 620 K with the corresponding value of $\sim$ 2.4 W/m-K. We have also carried out the theoretical calculations and the best matching between experimental and calculated values of transport properties are observed in spin-polarized calculation within DFT+\textit{U} by chosen \textit{U} = 4 eV. The maximum calculated value of ZT is found to be $\sim$ 0.67 at 1200 K for p-type conduction. Our computational study suggests that the possibility of n-type behaviour of the compound which can lead to a large value of ZT at higher temperature region. Electron doping of $\sim$ 5.1$\times$10$^{20}$ cm$^{-3}$ is expected to give rise the high ZT value of $\sim$ 2.7 at 1200 K. Using these temperature-dependent ZT values, we have calculated the maximum possible values of efficiency ($\eta$) of thermoelectric generator (TEG) made by p and n-type Na$_{0.74}$CoO$_{2}$. The present study suggests that one can get the efficiency of a TE cell as high as $\sim$ 11$\%$ when the cold and hot end temperature are fixed at 300 K and 1200 K, respectively. Such high values of ZT and efficiency suggest that Na$_{0.74}$CoO$_{2}$ can be used as a potential candidate for high-temperature TE applications

Physiological and molecular characterization of in vitro cultures of an endemic medicinal herb, Chlorophytum borivilianum, under abiotic stress

This investigation was carried out to evaluate the effects of abiotic stress on the in vitro cultures of Chlorophytum borivilianum. Regenerated plantlets were re-inoculated on media containing different concentrations of sodium chloride (0, 34.2, 68.4, 136.8 and 171.0 μM) and mannitol (0, 10.6, 21.3, 42.7 and 53.4 μM), and thus subjected to in vitro salinity and drought stress. Both salinity and drought conditions affected all the morphological parameters and decreased growth performance at a higher concentration of sodium chloride and mannitol, respectively. The chlorophyll content decreased with time, while proline and protein content increased in the in vitro stress plant. The control and stress tolerant plantlets were subjected to random amplified polymorphic DNA (RAPD) analysis using 24 random decamers primers. Only 15 RAPD primers showed polymorphism and a total of 52 polymorphic loci were scored. The control plants showed the highest similarity with the drought stress plantlet, while plant under salinity stress showed least similarity. Two groups were generated from the RADP data in the dendrogram after UPGMA cluster analysis based on Jaccard’s similarity estimates for the RAPD data. The 2 dimensional scaling by principal component analysis (PCA) was in agreement with the similarity index.Key words: Abiotic stress, proline, Chlorophytum borivilianum, salinity, mannitol, random amplified polymorphic DNA (RAPD) markers

Utilization of carbon and nitrogen sources by Streptomyces kanamyceticus M 27 for the production of an Anti bacterial antibiotic

We tested a number of carbon and nitrogen compounds for their effect on the production of an antibacterial antibiotic by Streptomyces kananmyceticus M27. Dextrose was found to be the most suitable carbon source, though maltose, sucrose, and soluble starch gave moderate yields. (NH4)H2PO4 and yeast extract were adequate nitrogen sources for antibiotic production. There was, however, no direct relation between the growth of the organism and antibiotic formation. The pH of the medium might be an important factor for antibiotic formation, as media giving high antibiotic yields showed an alkaline pH

Organic metabolites produced by Vibrio parahaemolyticus strain An3 isolated from Goan mullet inhibit bacterial fish pathogens

Identification and action of several antibacterial metabolites produced by a fish pathogen Vibrio parahaemolyticus strain An3 from marine ecosystem of Goa has been demonstrated. Antibacterial activity of the crude cell extract of the test bacterium has been evaluated against indicator pathogenic bacterial strains such as Acinetobacter sp. An2, Aeromonas hydrophila strain An4, Staphylococcus arlettae strain An1 and Alteromonas aurentia strain SE3 by agar well diffusion method which clearly demonstrated comparatively more significant inhibitory effect on indicator bacteria as compared to several commonly used antibiotics. Gas chromatography mass spectrometry (GC-MS) analysis of crude cell extract of the test organism interestingly revealed presence of indole, phenyl acetic acid, n-(3- methyl-1, 2, 4-oxadiazol-5-yl) - 1- pyrrolidine carboximidamide, pyrrolopyrazines, tetramethyl pyrazine and other important phenolic compounds which may be responsible for antibacterial activity against indicator microorganisms tested. It has been clearly demonstrated that V. parahaemolyticus strain An3 produced several medically important organic metabolites during cultivation suggesting it as a potential candidate for production of several antibacterial metabolites to control pathogenic bacterial strains causing serious fish and human diseases.Key words: Antibacterial, gas chromatography mass spectrometry, metabolites, pathogenic bacteria, welldiffusion

Experimental and computational approaches to study the high temperature thermoelectric properties of novel topological semimetal CoSi

Here, we study the thermoelectric properties of topological semimetal CoSi in the temperature range $300-800$ K by using combined experimental and density functional theory (DFT) based methods. CoSi is synthesized using arc melting technique and the Rietveld refinement gives the lattice parameters of a = b = c = 4.445 {\AA}. The measured values of Seebeck coefficient (S) shows the non-monotonic behaviour in the studied temperature range with the value of $\sim-$81 $\mu$V/K at room temperature. The $|S|$ first increases till 560 K ($\sim-$93 $\mu$V/K) and then decreases up to 800 K ($\sim-$84 $\mu$V/K) indicating the dominating n-type behaviour in the full temperature range. The electrical conductivity, $\sigma$ (thermal conductivity, $\kappa$) shows the monotonic decreasing (increasing) behaviour with the values of $\sim$5.2$\times 10^{5}$ (12.1 W/m-K) and $\sim$3.6$\times 10^{5}$ (14.2 W/m-K) $\Omega^{-1}m^{-1}$ at 300 K and 800 K, respectively. The $\kappa$ exhibits the temperature dependency as, $\kappa \propto T^{0.16}$. The DFT based Boltzmann transport theory is used to understand these behaviour. The multi-band electron and hole pockets appear to be mainly responsible for deciding the temperature dependent transport behaviour. Specifically, the decrease in the $|S|$ above 560 K and change in the slope of $\sigma$ around 450 K are due to the contribution of thermally generated charge carriers from the hole pockets. The temperature dependent relaxation time is computed which shows temperature dependency of $1/T^{0.35}$. Present study suggests that electronic band-structure obtained from DFT provides reasonably good estimate of the transport coefficients of CoSi in the high temperature region of $300-800$ K

Antibacterial activity of seed extracts of Argemone mexicana L. on some pathogenic bacterial strains

Antibacterial activity of seed extracts of Argemone mexicana L. (Papaveraceae) was evaluated against some pathogenic bacterial strains. Chloroform extract of seeds exhibited varying level of antibacterialactivity, with minimum inhibitory concentrations (MIC) of 2.0 - 5.0 mg/ml, against both Gram-positive and Gram-negative bacteria. The chloroform extract was found to be more active than the other extracts against all the test bacteria. MIC values were 2.0 and 3.0 mg/ml, respectively, for Staphylococcus aureus and Pseudomonas aeruginosa and their respective drug-resistant strains. The sensitivity of the test bacteria varied with the species and strains. The study provides basis for the isolation andpurification of antibacterial compound(s) from the seeds of A. mexicana L