الفهرس 
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Abstract
In the current study, root nodules were collected from three species of crop legumes (Vicia faba, Cicer arietinum, Trifolium resupinatum) obtained from Beni-Suef Governorate, Egypt. Also, one species of wild herb legumes (Vicia faba) was obtained from Minia governorate, Egypt, from 10-15 cm depth.
Legumes were gently uprooted and the root system was cleaned of sticky soil particles under running water and healthy intact pink nodules were selected. Surface sterilization of root nodules was performed. These ready nodule have been moved to a culture tube half full of sterile water and crashing to achieve a milky suspension with sterile glass rods.. Serial dilution was performed, followed by streaking on yeast extract mannitol (YEM) supplemented with Congo red (25 µg /mL) and incubated between two to three days at 28°C. A Gram stain technique was applied to identify collected Rhizobium isolates. All suspected isolates were stored in 40% glycerol at – 80ºC
Three reference Rhizobium strains were graciously provided by the Agricultural Research Centre, Giza, Egypt. These reference strains were used as controls to detect the validity of culture media and suitability of the used conditions for isolation of Rhizobium sp.
The bacterial strains were identified to be as Rhizobium under a microscope examination done after gram staining.
All isolated Rhizobium sp.(35 isolates) were allowed to grow in YEM media under different stress conditions, including 1%, 2%, 3%, 4% NaCl, and different adjusted pH (4, 6, and 8). The availability of each isolate to grow under these conditions was recorded. Two isolates of both ES-BM9 and ES-CS4 can survive under all tested concentrations.
The partial 16S rRNA gene sequencing of both isolates ES-BM9 and ES-CS4 revealed similarity 98.7% with Rhizobium leguminosarum and 99.2% with Rhizobium pusense, respectively.
Metabolites containing EXP were extracted later from these isolates and were tested for their anti-proliferative cytotoxicity via tissue culture technique against three selected cell lines; hepatocellular carcinoma cell line (HepG-2), human breast carcinoma cell line (MCF-7), and colorectal adenocarcinoma cell line (Caco-2).
Only ES-BM9 isolate showed potent anti-tumor cytotoxicity against all tested cell lines compared with that of ES-CS4 isolate at which the survival fractions were pointedly reduced as the concentration raised. The concentrations that cause a 50% growth inhibition (IC50) were calculated and revealed that the lowest recorded IC50 was against HepG-2 with 4.255 mg/ml.
LC -HRESIMS were done and revealed the presence of diverse compounds belonging to antimicrobials, antitumors, siderophores, exopolysaccharides, and other biologically significant metabolites. These compounds were compared with previously extracted compounds with using databases of various libraries.This is the first study to identify Octapeptin-A2, Fortimicin, Chalcomycin, and Lipopeptide NO being recovered from Rhizobium sp. and the first study to report antitumor activities from Rhizobium sp. isolated from Egypt.