الفهرس 
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Abstract
1- This study aims mainly to isolate and exploring actinobacteria associated with rhizosphere of some halophytes. 2- six locations were chosen to gather soil samples from the northern sector of the Nile Delta. 3- three soil samples were collected near plant roots at a depth of 10-15 cm and Its Biological Applications. 4- Through this study the soil samples were inoculated by serial dilution and 3 pure isolated were isolated by streak plate method. 5- Morphology is an important characteristic for the description of taxa, it is not adequate to differentiate between many genera. And in fact, it was the only characteristic used in many early descriptions. 6- The identification process was done using MALDI Biotyper (Bruker Daltonics GmbH & Co, Billerica, Massachusetts, USA). FlexControl and FlexAnalysis (Bruker Daltonics GmbH & Co, Bremen, Germany) were used for data acquisition and data processing, respectively. 7- Three isolated of actinomycetes (S1, S2 and S3) were identified, as the results of the morphological and MALDITOF identification showed for these strains. The aerial mycelium of the S1 strain was faint green, S2 and S 3 were dark and powdery green in color. All the isolates had no pigments on the selected medium. 8- MALDI-TOF MS analysis the identified species were Streptomyces violaceoruber LT55DB, Streptomyces nogalater LT7C87 and Streptomyces chartreusis LT55D0 with identification score 0.81, 0.82 and 0.62 respectively. 9- The phytochemical analysis of the selected halophytes samples growing naturally in coastal habitats in Egypt disclosed that MeOH extracts of these species are richer in bioactive compounds such as tannins and phenolics composition. According to phytoconstituent data, the following is the order of phytocomponents found in the plant species that have been studied: Zygophyllum coccineum ˃ Zygophyllum aegyptium ˃ Atriplex halimus. 10- the antioxidant properties of three selected plant extracts (A. halimus, Z. aegyptium and Z. coccineum) were in vitro evaluated by DPPH assay. Based on the results of IC50, the antioxidant activity of the four plant samples follows the sequence A. halimus ˃ Z. aegyptium ˃ Z. coccineum. 11- The antimicrobial efficiency of halophytes was assessed in vitro using different pathogenic strains. The Escherichia coli, MERSA and Salmonella typhi were the most affected bacterial strain, while Klebsiella pneumonia and Staphylococcus aureus were the most resistant to the MeOH of samples. According to their sensitivity, the organisms tested can be sequenced as follows: S. typhi > E. coli >MERSA > S. aureus > K. pneumonia. 12- the cytotoxic activities of the prepared plant samples extracts were evaluated using an MTT assay. The samples were tested in vitro against two tumor cells, i.e., HepG-2, and PC3 cell lines. Doxorubicin was selected as a reference drug. The IC50 values are inversely proportional to the efficiency of the sample to inhibit the growth of the cancer cells. Therefore, a potent cytotoxic agent would require low values of IC50. Based on the results of IC50, the cytotoxic activity of the three samples follows the Zygophyllum coccineum ˃ Zygophyllum aegyptium ˃ Atriplex halimus for HepG-2 and PC3 cell lines