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Abstract SUMMARY Tributyltin can be highly toxic to many eukaryotic and prokaryotic organisms and have also been identified as immune system inhibitor and endocrine disruptors in humans; it was used in antifouling paints to prevent fouling it’s also used in industrial purposes as biocide and preservative. The main purpose of this thesis was to isolate new bacterial strains able to degrade TBT into less toxic compounds (DBT&MBT) and to elucidate the mechanism of resistance to TBT. The obtained result can be summarized as follows: 1. Three bacterial strains were isolated; they have the ability to grow on TBT as sole source of carbon and energy from samples collected from the Mediterranean Sea in Abu Qir port, Alexandria, Egypt. 2. The three isolates were identified morphologically, biochemically and by the 16S rRNA gene sequence analysis, the isolates were identified as Sphingobiumsp.HS1 and StenotrophomonasspHS2. &RhizobiumborboriHS5. HS5 and were tested for antibiotic sensitivity. 3. The phylogenetic analysis of the isolated strains was constructed in comparison with other related organic compound degraders, by neighbor-joining distance analysis of their 16S rRNA gene sequence Stenotrophomonas sp HS2was highly similar to Stenotrophomonas chelatiphaga strain LPM-5in the GenBank, which is EDTAdegrading bacterium, and 98% with Stenotrophomonas maltophilia which is monocyclic hydrocarbon degrading bacterium. Summary 78 4. TBT sensitivity test was determined and Rhizobium borbori HS5 and Sphingobiumsp.HS1 were able to resist TBT up to 2Mm while Stenotrophomonas sp. HS2 was able to resist TBT up to 3Mm. 5. TBT used by Stenotrophomonas sp. HS2was analyzed using GC-FID (gas chromatography with flame ionization detector). 6. The phylogenetic analysis of the amplified fragment obtained using primer sets (sugEF, sugER2) was constructed in comparison with the other similar gene sequences from NCBI. It was found Arsenic efflux pump protein (homology 93%) with aryl sulfatase protien in Stenotrophomonas maltophilia and 87% homology with arsenic efflux pump protein in Xanthomonas oryzea. 7. Finally, These results suggest that it may be possible to expand the range of biodegradable TBT congeners and this leads to more accurate assessments of pollutant biodegradation and the impact of remediation technologies. |