Microbial synthesis of silver nanoparticles by streptomyces glaucus and spirulina platensis

Microbial synthesis of nanoparticles has a potential to develop simple, costeffective and eco-friendly methods for production of technologically important materials. In this study, for the first time a novelactinomycete strain Streptomyces glaucus71 MD isolated from a soy rhizosphere in Georgiais for the first time extensively characterized and utilized for the synthesis of silver nanoparticles. Scanning Electron Microscope (SEM) allowed observing extracellular synthesis of nanoparticles, which has many advantages from the point of view of applications. Production of silver nanoparticles proceeded extracellularlywith the participation of another microorganism, bluegreen microalgae Spirulinaplatensis (S. platensis). In this study it is shown that the production rate of the nanoparticles depends not only on the initial concentration of AgNO3 but also varies with time in a nonmonotonic way. SEM study of silver nanoparticles remaining on the surface of microalgae revealed that after 1 day of exposure to 1 mM AgNO3 nanoparticles were arranged as long aggregates along S. platensiscells strongly damaged by silver ions. However, after 5 days of exposure to silver S. platensiscells looked completely recovered and the nanoparticles were distributed more uniformly on the surface of the cells. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2067

A Calorimetric Characterization of Cr(VI)-Reducing Arthrobacter oxydans

This is the first of a series of calorimetric studies designed to characterize and understand survival mechanisms of metal-reducing bacteria isolated from metal-polluted environments. In this paper we introduce a new concept of thermal spectrum of the endothermic melting of complex biological systems (e.g., proteins, nucleic acids, ribosomes, membrane structures) in intact cells. All thermal spectra measured are thermograms that describe the temperature dependence of heat capacity change of the complex systems of biologically active substances in bacterial cells. This new concept of thermal spectrum was applied to investigate spectral features from intact cells of Cr(VI)-reducer Arthrobacter oxydans at different points of their growth conditions and stages. Over the temperature range of 40–105°C, we observed that spectral changes are particularly significant in the 40–90°C interval. This may correspond to the orderly changes in subcellular structural elements: proteins, ribosomes and RNA, membranes, and various structural elements of the cell wall during different points of the growth cycle and growth conditions. Spectral changes in the 90–105°C region are less pronounced, implicating that the structural composition of DNA-Protein (DNP) complexes may change little

EPITHERMAL NEUTRON ACTIVATION ANALYSIS FOR BACTERIAL TRANSFORMATIONS OF CHROMIUM

Most powerful primary analytical technique, neutron activation analysis, was applied to study indigenous bacteria, namely, Arthrobacter genera which can be successfully used in detoxification and immobilization of toxic substances. In the present study the effect of Cr(VI) on the elemental content of these bacteria has been examined. The concentrations from 12 to 19 elements such as Na, Al, Cl, K, Fe, Co, Zn, As, Br, Rb, Sr, Sb, Ba, Tb, Th, U were determined in the bacterial cells. The high rate of Cr accumulation in the tested bacterial cells was shown. In bacteria treated with chromate some similarity in the behaviour of the following essential elements − potassium, sodium, chlorine − was observed. Such non-essential elements as Ag, As, Br and U were determined in all bacteria and have to be considered by cells as toxins