Siderophore production by a marine Pseudomonas aeruginosa and its antagonistic action against phytopathogenic fungi

A marine isolate of fluorescent Pseudomonas sp. having the ability to produce the pyoverdine type of siderophores under low iron stress (up to 10 μM iron in the succinate medium) was identified as Pseudomonas aeruginosa by using BIOLOG Breathprint and siderotyping. Pyoverdine production was optimum at 0.2% (w/v) succinate, pH 6.0, in an iron-deficient medium. Studies carried out in vitro revealed that purified siderophores and Pseudomonas culture have good antifungal activity against the plant deleterious fungi, namely, Aspergillus niger, Aspergillus flavus, Aspergillus oryzae, Fusarium oxysporum, and Sclerotium rolfsii. Siderophore-based maximum inhibition was observed against A. niger. These in vitro antagonistic actions of marine Pseudomonas against phytopathogens suggest the potential of the organism to serve as a biocontrol agent.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Facile,single-pot preparation of nanoporous SiO2 particles (carrier) with AgNPs at core and crust for controlled disinfectant release

This study demonstrates a novel, facile and one-pot approach to synthesize silica nanoparticles with silver at core and crust (SiNP-AgCC). A modified Stöber method was used to make SiNP-AgCC. A significant reduction in the size of SiO₂ nanoparticles was seen, with 2–5 nm AgNPs being uniformly distributed on the surface and 10–20 nm AgNPs in the center. A typical mesoporous SiO₂ particle (SiNP) produced using the Stöber method was transformed to nanoporous SiO₂ by this modified Stöber method. Nanoporous SiO₂ particles with silver in the center are advantageous for slow and consistent Ag⁺ release, which was confirmed by Ag⁺ ion release test. Antibacterial activities of the samples were tested to evaluate the disinfection performance of the samples on gram-negative bacteria (Escherichia coli) using disk diffusion and the LB-agar method. SiNP-AgCC showed prolonged silver release for more than 20 days and improved antibacterial properties even after five days of incubation.     

Siderophoregenic Bradyrhizobia boost yield of soybean

After screening for siderophore (microbial iron chelator) production, of seven available cultures of soybean (Glycine max L.) root nodule bradyrhizobia, one strain, Bradyrhizobium japonicum NCIM 2746, was selected to confirm its phytopathogenic suppression and soybean growth promotion. Based on chromatographic and spectrophotometric studies, two different siderophores, a hydroxamate type (MW 734) and another catecholate type (MW 1000), were observed. Randomized block design (RBD) analysis of sickpot studies (soil inoculated with phytopathogens) with an MACS 124 variety of soybean, bacterized with siderophoregenic B. japonicum, showed a marked increase in the percentage of germination, nodulation, chlorophyll, oil, protein content, and number of pods. Field trial study confirmed these pot results, which were evident from enhancement in shoot length, number of branches, chlorophyll content, number of nodules, root length, and number of pods. These results suggest the possibility of exploiting B. japonicum NCIM 2746 as a potential bioinoculant.     

The Microbial Pathology of Neu5Ac and Gal Epitopes

Glycans play a vital role in modulating many physiological and pathological phenomena of microbes and humans, such as bacterial adhesion, colonization, host-microbial interactions, cancer recognition, and blood group determination. The aim of the current review is to provide an account of the functions of N-acetyl sialic acid (Neu5Ac) and galactose (Gal) residues in microbial pathology. Specifically, an overview of the biosynthesis and metabolism of Neu5Ac and Gal residues in different bacterial species will provide a better understanding of microbial pathogenesis in the human body.     

Elastic properties of the Ta–V system: bcc Ta0.33V0.67 and C15 TaV2

Resonant ultrasound spectroscopy was used to measure the elastic constants of bcc Ta_0.33V_0.67 over the temperature range 3.5–300?K; the results were compared to earlier measurements on C15 TaV₂. The temperature dependence of the polycrystalline shear modulus is completely different in the two phases; that of the bcc phase decreases with temperature whereas that of the C15 phases increases in an anomalous fashion. This difference is consistent with a model involving doubly-degenerate levels at the X point of the Brillouin zone in the C15 phase with the Fermi level lying near the doubly degenerate level. This model accounted for the unusual behaviour of the C15 phase. Debye temperatures were determined from the ultrasonic measurements: 295?K for the C15 phase and 315?K for the bcc phase.     

Synthesis and physico-chemical properties of copoly(ester-sulfonates) of 1,1-bis (3-methyl-4-hydroxy phenyl) cyclohexane with 2,4-toluene disulfonyl and terephthaloyl chlorides

Copoly(ester-sulfonates) of varying compositions have been synthesized by interfacial polycondensation technique by using H₂O-CHCl₃ as an interphase, alkali as an acid acceptor and sodium lauryl sulfate-cetyl trimethyl ammonium bromide as mixed emulsifiers at 0 °C for 4 h. Copolymers are characterized by IR and NMR spectral data, viscosity in three different solvents at three temperatures and little solvent and temperature effect is found on [η]; and density (1.3430-1.3406 g/cm³) by floatation method. Copolymers possess excellent solubility in common solvents and chemical resistance against water, acids, alkalis and salts. They possess moderate to good tensile strength (10.6-79.5 N/mm²), excellent volume resistivity (7.5-28 × 10¹⁶ Ω cm), electric strength (53-118 kV/mm) and dielectric constant (1.3-1.58). They are thermally stable up to about 349-373 °C in an N₂ atmosphere and possess high T_g (136-196 °C). DTA endo/exothermic transitions supported either decomposition or formation of new product(s). Physical properties of copolymers are improved with increasing terephthlate content.