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The present study aims to search for a nano-delivery system that enables access of antimicrobial compounds to the targeting site of the microbial pathogens. To achieve this objective, the antimicrobial compounds extracted from the local isolate Streptomyces rimosus were loaded on chitosan (CS) and calcium phosphate (CaP) nanoparticles (NPs) to facilitate drug delivery to some species of bacteria (Escherichia coli ATCC25922, Staphylococcus aureus ATCC25923 and Bacillus cereus ATCC6633) and the yeast Candida albicans ATCC10231. The best incubation period for the production of antifungal and antibacterial compounds, pH, temperature, carbon sources and nitrogen sources were around the third day, 7.0, 30°C, starch and potassium nitrate, respectively. The extracted compounds were identified using gas chromatography-mass spectrometry (GC-MS) analysis which revealed to the identification of nine antimicrobial organic acids. The prepared NPs were characterized using transmission electron microscopy (TEM) and Zeta potential analyser. Results showed those chitosan nanoparticles (CSNPs) were spherical shaped NPs with an average size ≈22 ± 2 nm. The CSNPs loaded with the antimicrobial molecule’s diameter was ranged from 55 upto 100 nm. Calcium phosphates nanoparticles (CaPNPs) were also spherical shaped NPs with diameter range from 70 to 95 nm. Loading of antimicrobial compounds onto CaPNPs made them appeared in rod shape with width varying from 14 to 27 nm and length from 274 to 397 nm. The synthesized NPs showed negative values confirming their high dispersity and long-term stability. The tested strains were resistant to solo NPs; but the loaded NPs with the extracted antimicrobial compounds, particularly the CaPNPs, augmented the potency of the isolated antimicrobial compounds, with emergence of differential antimicrobial activity. The activity of the NPs-bound antimicrobial compounds was more evident against bacteria than fungi, Gram-positive bacteria than Gram-negative bacteria and against B. cereus than S. aureus.

Siwa Oasis represents a promising area for agricultural expansion projects in the western desert of Egypt due to the availability of water resources. However, these areas are suffering from land degradation problems, especially soil salinity. Accordingly, the main objectives of this work were to evaluate and map soil salinity as well as groundwater quality in Siwa Oasis. Therefore, twenty representative soil profiles were randomly distributed throughout the studied area. These profiles were sampled based on the development of soil horizons. A total of 46 soil-samples were collected and these samples were analyzed for their physical and chemical properties. Groundwater samples were collected from irrigation-wells and they were analyzed for their chemical parameters. Landsat images were also acquired at three different periods to monitor the changes in vegetation cover, soil salinity and water logging. The obtained results indicated a wide variability within soil physical and chemical properties in the Oasis. Most of the suited soils were very saline, non-sodic based on the EC and ESP values (EC= 77 dSm-1 and ESP= 14.62 in average). Agricultural areas were increased from 22 km 2 in 1992 to 81 km 2 in 2015. On the other hand, saline soils were increased from 35 km 2 to 64 km 2 and water logged areas were also increased from 19 to 51 km 2 from 1992 to 2015, respectively. These results could be due to the expansion in reclamation-projects, increase in crop irrigation and poor drainage. The salinity of groundwater varied from 2.28 to 5.45 dSm-1 (3.76 in average), which indicates a degradation in its quality. In summary, soils in Siwa Oasis are salt-affected and they need a proper land reclamation program and development of effective irrigation and drainage systems.

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