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 WM and V max of 2.5 Wmol min 31 mg 31 . Optimal activity occurred at pH 9.5 and 150 g l 31 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.

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.

A soluble c-type cytochrome was first purified from Geobacter metallireducens to an electrophoretically homogeneous state. The purified cytochrome c showed absorption peaks at 530 and 409 nm in the oxidized form and 552, 522, and 418 nm in the reduced form. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate allowed us to calculate the molecular mass at 9.5 kDa. It contained 3 mol of heme c per molecule of the protein on the basis of heme c and protein concentration. The mid-point redox potential at pH 7.0 was determined to be 3190 mV. Although the N-terminal amino acid sequence of the first 17 residues was similar to that of Desulfuromonas acetoxidans cytochrome c U , G. metallireducens cytochrome c did not show Fe(III)-reducing activity. z

Twenty out of 400 isolates of bacteria mainly from salt marshes and saline soils of Egypt were successfully grown on mannitol N-free medium. The nitrogen-fixing activity was then demonstrated for the twenty isolates in modified STANIER'S medium using the acetylene reduction assay. All of them possessed appreciable nitrogenase activity (acetylene reduction) under non-saline conditions ; however, at 5% NaCl only 60% of the isolates exhibited a high rate of this activity and 25% were completely negative under these conditions. The bacterial isolates grew well in STANIER'S medium; nevertheless, growth of the majority of isolates was reduced by about 30-80% in the same medium containing 5 % NaCl. Cellulolytic activity was detected in 60% of the twenty strains, amylolytic in 45%, and pectinolytic in 10% of the isolates. The bacterial isolates showed also enzymatic activity under saline conditions (5 % NaCl). The preliminary identification indicated that six isolates were Gram positive spore-forming bacteria of the genus Bacillus, the others were Gram negative rods which remain to be identified.

Background Bacillus thuringiensis (Bt) produces a group of δ-endotoxin proteins designated as cry toxins. No doubt that Bt isolates are excellent potential candidates for biological control strategies. Results The present study showed that 12 Bt strains were isolated and characterized at morphological, biochemical, and molecular levels. All the tested 12 Bt strains were gram-positive, endospore-forming, and possessing typical Bt crystal structures under the scanning electron microscopy (SEM). Universal primers direct and reverse of five pairs were used to detect five Cry-type genes (Cry1, Cry2, Cry3, Cry4, Cry7, and Cry8) by the PCR sizes produced from the studied Bt strains. The 16S rRNA PCR technique, 16S gene primer, DNA template, dNTPs, and Taq polymerase produced unique and distinguishable restriction patterns used for the molecular characterization of the studied Bt strains. Based on the PCR products, the frequency of Cry-gene distribution among the tested strains was Cry1 100%, Cry4 85%, and Cry3 62%, and Cry2 and Cry7 frequency was 54%. Based on the activity of insecticidal of the tested Bt strains, Bt1, Bt9, Bt10, and Bt11 were extremely pathogenic; their pathogenicity ranged from 93 to 100% against dipteran and lepidopteran larvae, compared to the other Bt isolates. The nucleotide sequences of amplified 1500 bp conserved region of 16S rRNA genes of four strains blasted using NCBI database compared to NCBI database sequences, and they were reported as native strains of Bt showing high homology with the known Bt strains (99–100%). The nucleotide sequences of Bt1, Bt9, Bt10, and Bt11 were placed in the GenBank database under accession numbers MN860017, MN843958, MN843959, and MN843960, respectively. Conclusion The strategies of enhancing the sustainability of crops and vegetables that are targeted by a large number of pathogenic insects require a great effort of exploring novel species and strains of Bt. Herein, native strains of Bt were documented from the eastern province of Saudi Arabia that displayed bio-insecticidal action on larvae of Diptera and Lepidoptera.

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