The respiratory arsenate reductase from the Gram-positive, haloalkaliphile, Bacillus selenitireducens strain MLS10 was purified and characterized. It is a membrane bound heterodimer (150 kDa) composed of two subunits ArrA (110 kDa) and ArrB (34 kDa), with an apparent K(m) for arsenate of 34 microM and V(max) of 2.5 micromol min(-1) mg(-1). Optimal activity occurred at pH 9.5 and 150 g l(-1) of NaCl. Metal analysis (inductively coupled plasma mass spectrometry) of the holoenzyme and sequence analysis of the catalytic subunit (ArrA; the gene for which was cloned and sequenced) indicate it is a member of the DMSO reductase family of molybdoproteins.

Iron nanoparticles (FeNP) were synthesized using Acacia nilotica seedless pods extract. The synthesized FeNP were characterized by Fourier transform infrared (FTIR), UV/Vis spectroscopy, dynamic light scattering (DLS), electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The XRD pattern confirmed the synthesis of crystalline phase of α-Fe₂O₃. EDS spectroscopy showed the presence of elemental iron and oxygen, indicating that the nanoparticles are essentially present in oxide form. UV absorption in the range of 450–550 nm confirmed the formation of FeNP. DLS indicated an average FeNP particle size of 229 nm. The synthesized FeNP was tested for adsorption and oxidation degradation of methyl orange (MO) under different conditions and found to be effective in both degradation and adsorption processes. Furthermore, the synthesized FeNP has the potential to terminate the pathogenicity of several human opportunistic pathogens; belongs to gram-negative and gram-positive bacteria and one species of Candida as well.

Problems statement: The disturbance of aquatic ecosystems provoked by heavy metals pollution from industrial and domestic sources, has as consequence the loss of biological diversity, as well as increased bioaccumulation and magnification of toxicants in the food chain. The aim of this study was to evaluate the effect of some heavy metals on some physiological activities of Chlorella vulgaris beyerinck with special references to metal bioaccumulation. Approach: Chlorella vulgaris Beyerinck was isolated from Al-Asfar Lake, Al-Hassa, Saudi Arabia. A standard initial inoculum of the isolated algae was inoculated to culture flasks. The culture flasks were supplied with various concentrations of Cobalt, Copper and Zinc ranging from 10-6-10-9 M. At the end of the incubation period cultures were filtered and washed several times by distilled water for measurements the various experimental parameters. Results: The data show that the lower doses of the three tested metals had stimulatory effect in biomass yield of Chlorella vulgaris, whereas the higher doses were inhibitory depending on the type of the metal. The inhibitory effect of copper to the growth parameters of Chlorella vulgaris was more pronounced than other two tested metals. The total protein content, total carbohydrate and the total free amino acids of the tested green alga Chlorella vulgaris gradually decreased in a manner dependent on the metal concentration in the medium. On the other hand, bioaccumulation of cobalt, copper and zinc by Chlorella vulgaris cells were parallel to increasing the concentrations in the culture medium. Conclusion: The inhibitory and stimulatory effects of either of the used heavy metals depend on concentration. Different organisms, however, have different sensitivities to the same metal and the same organisms may be more or less damaged by different metals. The uptake of an element from the surrounding medium is seldom exactly proportional to the amount present in the water.

Background: Metal reduction is thought to take place at or near the bacterial outer membrane and, thus, outer membrane proteins in the model dissimilatory metal-reducing organism Geobacter sulfurreducens are of interest to understand the mechanisms of Fe(III) reduction in the Geobacter species that are the predominant Fe(III) reducers in many environments. Previous studies have implicated periplasmic and outer membrane cytochromes in electron transfer to metals. Here we show that the most abundant outer membrane protein of G. sulfurreducens, OmpJ, is not a cytochrome yet it is required for metal respiration. Results: When outer membrane proteins of G. sulfurreducens were separated via SDS-PAGE, one protein, designated OmpJ (o uter m embrane p rotein J), was particularly abundant. The encoding gene, which was identified from mass spectrometry analysis of peptide fragments, is present in other Geobacteraceae, but not in organisms outside this family. The predicted localization and structure of the OmpJ protein suggested that it was a porin. Deletion of the ompJ gene in G. sulfurreducens produced a strain that grew as well as the wild-type strain with fumarate as the electron acceptor but could not grow with metals, such as soluble or insoluble Fe (III) and insoluble Mn (IV) oxide, as the electron acceptor. The heme c content in the mutant strain was ca. 50% of the wild-type and there was a widespread loss of multiple cytochromes from soluble and membrane fractions. Transmission electron microscopy analyses of mutant cells revealed an unusually enlarged periplasm, which is likely to trigger extracytoplasmic stress response mechanisms leading to the degradation of periplasmic and/or outer membrane proteins, such as cytochromes, required for metal reduction. Thus, the loss of the capacity for extracellular electron transport in the mutant could be due to the missing c-type cytochromes, or some more direct, but as yet unknown, role of OmpJ in metal reduction. Conclusion: OmpJ is a putative porin found in the outer membrane of the model metal reducer G. sulfurreducens that is required for respiration of extracellular electron acceptors such as soluble and insoluble metals. The effect of OmpJ in extracellular electron transfer is indirect, as OmpJ is required to keep the integrity of the periplasmic space necessary for proper folding and functioning of periplasmic and outer membrane electron transport components. The exclusive presence of ompJ in members of the Geobacteraceae family as well as its role in metal reduction suggest that the ompJ sequence may be useful in tracking the growth or activity of Geobacteraceae in sedimentary environments.

Ulcerative colitis (UC) is a gastrointestinal inflammatory disease with a multifactorial pathophysiology. This study aims to investigate the immunomodulatory effect of Portulaca oleracea leaf ethanolic extract (POE) on acetic acid (AA)-induced UC in mice. Experimental animals received oral doses of POE (200 mg/kg for 7 days) after an induction of colitis by intrarectal AA administration. In mice with AA-induced UC treated with POE, the results revealed a significant modulation in body weight and colon length. Moreover, treatment with POE downregulated the interleukin 1, 6, and 17, tumor necrosis factor-alpha, gamma interferon, and nuclear factor-kappa B levels compared with the colitis group. Furthermore, POE markedly inhibited histological damage, decreased myeloperoxidase activity and reduced fecal calprotectin level compared with the colitis group. These data are consistent with the reduction in total bacterial content in the colon. Taken together, treatment with POE may reduce colonic inflammation by alleviating the immune response and inhibiting the severity of colitis. The HPLC analysis of POE resulted in the identification of seven medicinal compounds comprising two phenolic acids (ferulic and caffeic acids) and five flavonoids (kaempferol, quercetin, rutin, narenginin and hesperidin). Subsequent analysis of POE by GC-MS revealed ten phytocomponents; the major percentages were hexadecenoic acid, methyl ester (29.8119%), α-linolenic acid (25.8431%), 16-octadecenoic acid, methyl ester (15.1578%) and α-tocopherol (10.7848%). Delta-lactams and alkanes were the minor components. Such natural plant-derived substances and their probable synergistic action appear to contribute to a promising therapeutic protocol for colitis.