Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Microbiology

This study aims at identifying the types of organic pollutants (PAHs) in sea water and the River Nile in Egypt, treating them and getting rid of them safely via isolating microbial strains that can degrade such pollutants. Samples collected from the Red Sea, the Mediterranean and the River Nile were evaluated chemically and microbiologically.Chemical analysis showed that the pH slightly changed according to the sampling site.This was accompanied by changes in EC and TDS. Sea water samples scored high concentrations of anions and cations. The sodium ion was the prevalent cation in all samples. An increase in the total viable microbial counts (1.6 x 104 cells/ml) was recorded in the GCB-19 sample collected from Cairo University Nile Bus Station (Giza), and the highest count of fecal coliforms was detected both in this sample and in GCB-17 and CMB-19 (95 cells/ml). Sea water samples revealed high PAHs concentrations in comparison with the River Nile water ones. Fluorene was detected in all samples, ranging from 25 to 50 ppt. The results showed that naphthalene{u2019}s concentration came highest (240 ppt), compared with the other PAHs in all samples. Nineteen microorganisms were isolated from water samples; their preliminary morphological identification was conducted through microscopic examination. The PAHs (napthalene, fluorene and anthracene) degradation efficiency of the microbial isolates was determined at different concentrations (200, 500 and 1000 ppm). Four microbial isolates showed the highest capability of degradation for the tested PAHs at 1000 ppm with degradation percentage reached to 99.99%.The total counts of the microbial isolates, tested in degrading fluorene, naphthalene and anthracene at 200, 500 and 1000 ppm, decreased at the end of the biodegradation experiment with no significant differences between their dry weights. The four microbial isolates were identified through molecular identification tools as follows: Leclercia adecarboxylata, Penicillium rubens, Bacillus tequilensis and Bacillus velezensis. The antimicrobial activity of the tested microbial strains in the PAHs degradation was evaluated against four pathogenic microorganisms (E. coli, S. aureus, P. aeuroginosa , S. typhimurium). S. aureus was the microbe most sensitive to the microbial cultures and extracellular extracts of L. adecarboxylata and B. tequilensis

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