Antimicrobial activity of potato Rhizospheric Pseudomonas chlororaphis subsp. aureofaciens from Sétif Algeria

Aims: This study was assessed to demonstrate the antimicrobial activity in vitro of an identified fluorescent Pseudomonas strain characterized for its capacity to produce phenazine compounds. Methodology: First Pseudomonas chlororaphis subsp aureofaciens was inoculated on Nutrient Broth supplemented with Yeast Extract (NBY) and with glucose at a final concentration of 2%, after incubation the filtered culture was acidified with HCl to pH 2. The solution was extracted twice with the same volume of ethyl-acetate. The organic supernatants were combined, dried over anhydrous Na2SO4, and evaporated to dryness. The crude extract was resuspended in methanol and tested for antimicrobial activity. Antimicrobial activity was determined (i) by disc diffusion technique for bacteria and (ii) using serial dilution technique in soft PDA for fungi. Secondly the antifungal activity of the bacterial strain was tested against several phytopathogenic fungi in dual culture. Results: The studied strain has an important activity against the phytopathogenic bacteria and fungi tested. Among the tested fungi Fusarium oxysporum f. sp. albedinis is the most sensitive to the actions of this Pseudomonas, where the inhibition rate reached 77.78%. The less sensitive one was Pythium ultimum with a rate of 55.56%. While for pathogenic bacteria only Salmonella enteridis was sensitive to the tested strain. Conclusion: Pseudomonas chlororaphis subsp aureofaciens showed appreciable antagonistic activity, in vitro, against special forms of Fusarium oxysporum and the tested phytopathogenic bacteria

Bacteriocins contributing in Rhizospheric competition among Fluorescent Pseudomonads

Aims: To examine the production of bacteriocins through the study of a group of rhizospheric Pseudomonas isolates already known to produce metabolites that are antagonistic to fungi. Methodology: Fourteen rhizospheric strains of fluorescent Pseudomonads spp., were tested as well as two referenced strains Pseudomonas protogens CHA0 and Pseudomonas aureofaciens 30-84, for their ability to produce induced bacteriocins. The induction is carried out first by UV light, and secondly by mitomycin C. Results: In addition to the reference strains, six isolates were found to produce bactericidal substances after UV light induction against Pseudomonas target bacteria but also against other genera (Escherichia and Staphylococcus). Producing strains were treated with mitomycin C, and then lysed with chloroform. Analysis of the lysates by trypsin and freezing treatments, suggests that the active compounds are of high molecular weight. Conclusion: It is therefore suggested that these bacteria could be good competitors for their introduction as biocontrol agents

Вплив легування міддю та температури відпалу на структурні, морфологічні та оптичні властивості тонких плівок NiO

Метою даної роботи є вивчення впливу легування міддю та температури відпалу на структурні, морфологічні та оптичні властивості тонких плівок оксиду нікелю (NiO). Тонкі плівки NiO, леговані Cu, були нанесені на скляні підкладки при температурі 350 °С методом спрей-піролізу. Гексагідрат хлориду нікелю NiCl2·6H2O, деіонізована вода та мідь використовувались відповідно як прекурсор, розчинник та домішка після відпалу плівок при температурах 400, 450, 500 та 550 °C. Рентгенівські дифрактограми (GIXRD) показали, що плівки NiO:Cu є полікристалічними з ГЦК структурою та переважним напрямком орієнтації вздовж [200], що відповідає значенню 2θ приблизно 43°. Візуалізація атомно-силової мікроскопії (AFM) виявила, що на поверхневу морфологію впливає додавання Cu, а середня шорсткість збільшується від 5,17 нм до 99,03 нм, коли швидкість легування змінюється від 2 % до 6 %. Оптичний коефіцієнт пропускання зменшується з 85 % до 65 % при збільшенні концентрації легування міддю плівок NiO, відпалених при 550 °C, а оптична ширина забороненої зони зміщується у синій діапазон з 3,63 еВ до 3,82 еВ.The aim of this work is to study the influence of copper doping and annealing temperature treatment on structural, morphological and optical properties of nickel oxide (NiO) thin films. Cu doped NiO thin films were deposited on glass substrates at 350 °C by spray pyrolysis technique. Nickel chloride hexahydrate NiCl2·6H2O, deionized water and copper were used as precursor, solvent and dopant source respectively after annealing at different temperatures of 400, 450, 500 and 550 °C. The grazing incidence X-ray diffraction (GIXRD) patterns revealed that NiO:Cu films are polycrystalline with face centered cubic structure and preferred orientation direction along [200] corresponding to 2θ value of approximately 43°. Atomic force microscopy (AFM) visualization revealed that surface morphology was found to be influenced by incorporation of Cu and average roughness increases from 5.17 nm to 99.03 nm when the doping rate varied from 2 % to 6 %. The optical transmittance decreases from 85 % to 65 % with the increase in Cu doping concentrations of NiO films annealed at 550 °C and the optical band gap was blue-shifted from 3.63 eV to 3.82 eV