Aim The aim of this study was to isolate potential molybdate‐reducing bacteria to be used for bioremediation. Methods and results Two molybdate‐reducing bacteria (Mo1 and MoI) were isolated from polluted soil samples from Ismailia Canal, Egypt and Sallah Elddin Governorate, Iraq respectively. The isolates exhibited dark blue colonies when grown on solid medium containing sodium molybdate which indicated the reduction of molybdate to molybdenum (Mo) blue. The absorbance values at 865 nm were 0·743 ± 0·007 and 0·453 ± 0·005 for Mo1 and MoI respectively. The Mo blue produced showed characteristic absorption spectrum peak at 865 nm and a shoulder at 700 nm. The isolates were identified by 16S rRNA genes sequencing and were submitted to GenBank as Raoultella ornithinolytica strain Mo1 and Raoultella planticola strain MoI. The optimum conditions were glucose as electron donor, initial pH of 6 and incubation temperature of 30°C. Scanning electron micrographs were taken for both isolates in the presence and absence of molybdate source. Conclusion To the best of our knowledge, this is the first recordation of molybdate reduction by Raoultella sp. isolated from Egypt and Iraq. Significance and Impact of the Study The isolated bacteria belonging to the Raoultella could be used in in situ bioremediation.

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Biological synthesis of nanoparticles is a promising approach that is comparatively inexpensive and eco-friendly. Among various microorganisms, actinobacteria have been found to be efficient in the synthesis of nanomaterials. In thisstudy, extracellular biosynthesis of silver nanoparticles (Ag-NPs) was investigated by mixing silver nitrate with culture filtrate of Streptomyces rochei strain MFA-37.The biosynthesized Ag-NPs were characterized by UV-Vis spectrophotometric analysis, and showed a peak of absorbance at 440 nm. Fourier transform infrared (FTIR) analysis showed amines and amides that are responsible for the stabilization of Ag-NPs. The morphology and size of nanoparticles were determined using high-resolution transmission electron microscopy, XRD and DLS techniques which indicated well dispersed, spherical Ag-NPs sized 2-20 nm, and the zeta potential of AgNPs reached-20.5 mV. Enhancement of antibacterial activity of fourteen antibiotics was conducted by combining antibiotics with synthesized AgNPs. The synergistic activities of AgNPs combination with antibiotics were determined using disc diffusion against two multi-drug resistant Staphylococcus aureus SA-185 and SA-325 recovered from Libya. The highest synergistic effects were 6.11 and 6.37 folds for Penicillin followed by 6.11 and 4.44 folds for Ciprofloxacin and 6.11 and 3.69 folds for Erythromycin for MRSA-185 and MRSA-325 , respectively. This activity of AgNPs and antibiotics could be valuable for the manufacture of hybrid drugs to kill or inhibit the MRSA infection especially in case of superficial injuries.