Bioaccumulation of 137Cs and 60Co in freshwater plants

Contamination of the aquatic environment by the heavy metals and radionuclides has become a serious concern in the world. In our study, gamma-spectrometry of freshwater plants Bacopa monnieri and Egeria densa growing in cultivation media spiked with 137CsCl and 60CoCl2 was used for quantitative determination of bioaccumulation kinetic and distribution Cs+ and Co2+ ions in plant tissues. We found, that bioaccumulation of Cs and Co by fully immersed B. monnieri in Hoagland media (HM) was dependent on ion concentration in medium. Approx. 5-times lower Cs uptake 2.9 nmol/g (d.w.) was obtained in plants cultivated in 20% HM than from deionized water. The maximal Co uptake was 4-times higher than cesium uptake at the same conditions. Both Cs and Co were localized mainly in roots. The highest immobilization from roots to shoots was found in the case of Co uptake from deionized water with concentration ratio [Co]leaves : [Co]stem : [Co]root = 1.00 : 5.33 : 56.8. Cesium uptake by submerged plant E. densa was also strongly dependent on nutrients concentration in medium. However, in the case of cobalt uptake this dependence was less pronounced. Nutrients concentration also had a significant influence on distribution of Cs between stems and leaves of E. densa. Cesium was localized in leaves, however with increasing of nutrients concentration in cultivation media Cs was localized for account of stem. On the other hand, cobalt was immobilized mainly in leaves in whole range of nutrients concentration. Obtained data can serve as a models for understanding of phytoaccumulation of radionuclides from open water ponds and water channels in the vicinity of nuclear power plants and monovalent and bivalent metals from industrial sources of contamination.

Crystal structures of two isostructural bivalent metal N-benzoylglycinates

The crystal structures of two coordination compounds of N-benzoylglycine, viz. catena-poly[[[diaquabis(N-benzoylglycinato)cobalt(II)]-μ-aqua] dihydrate], {[Co(C9H8NO3)2(H2O)3]·2H2O} n , 1, and catena-poly[[[diaquabis(N-benzoylglycinato)nickel(II)]-μ-aqua] dihydrate], {[Ni(C9H8NO3)2(H2O)3]·2H2O} n , 2, are described. The structures of 1 and 2 were reported previously [Morelock et al. (1979). J. Am. Chem. Soc. 101, 4858–4866] and redetermined in this work to determine the H-atom coordinates. In the isostructural compounds, the central metal is located on an inversion centre and exhibits a distorted octahedral geometry. A pair of terminal aqua ligands disposed trans to each other and a pair of monodentate N-benzoylglycinate ligands form the square base and account for four of the six vertices of the octahedron. A μ2-bridging aqua ligand links the bivalent metals into one-dimensional chains extending along the c-axis direction. The one-dimensional chains stabilized by O—H...O hydrogen bonds are interlinked by N—H...O and C—H...O hydrogen-bonding interactions.

Evaluating the Effect of Metal Interference in Inhibition of Biofilm Formation by Uropathogenic Escherichia coli Isolated From Hospitalized Patients

Introduction: Bacteria that are able to form biofilms can lead to chronic antibiotic-resistant infections and immunomodulatory effects. Iron and other bivalent metals are essential requirements for biofilm formation by bacteria. Escherichia coli is the most predominant agent causing urinary tract infection (UTI). This study aimed to assess the effects of bivalent metals (iron, zinc, cobalt, and copper) on biofilm formation by E. coli isolated from hospitalized patients suffering from UTI. Methods: A total of 110 E. coli were isolated from 200 UTI patients referred to Farmanieh hospital in Tehran, Iran. E. coli was confirmed by culture specific media, biochemical tests, and polymerase chain reaction (PCR) analysis. To determine the antibiotic resistance, the Kirby-Bauer disk method was used and the biofilm formation was assessed using microtiter plate assay and electron microscopy. Finally, the data were analyzed via paired t test using the SPSS software. Results: Based on our results, out of 110 urine samples containing E. coli, the highest and the lowest resistance were observed to ampicillin (90%) and amikacin (53%), respectively. The biofilm development was intensified in the presence of glucose and iron. The results also indicated that biofilm formation was inhibited by the use of bivalent metal ions including zinc, cobalt, and copper, with the maximum effect obtained for zinc (P < 0.05).Conclusion: Our work led us to conclude that zinc, cobalt, and copper can inhibit biofilm formation by bacterial strains in medicine.

SYNTHESIS, CHARACTERIZATION AND THERMAL BEHAVIOUR OF SOLID 2- METHOXYCINNAMYLIDENEPYRUVATE OF SOME BIVALENT METAL IONS IN CO2 AND N2 ATMOSPHERES

Solid State M-2-MeO-CP compounds, where M stands for bivalent metals (Mn, Fe, Co, Ni, Cu and Zn) and 2-MeO-CP is 2-methoxycinnamylidenepyruvate, were synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), elemental analysis and complexometry were used to establish the stoichiometry and to study the thermal behaviour of these compounds in CO and N atmospheres. The results were consistent with the general formula: M(L) ·H O. In 2 2 2 2 both atmospheres (CO , N ) the thermal decomposition occurs in consecutive steps which are characteristic of 2 2 each compound. For CO atmosphere the final residues were: Mn O , Fe O , Co O , NiO, Cu O and ZnO, while 2 3 4 3 4 3 4 2 under N atmosphere the thermal decomposition is still observed at 1000 º C.