الفهرس 
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Abstract
Aromatic compounds are considered as hazardous environmental pollutants specially BETX compounds (Benzene, toluene, ethyl benzene and xylene) they are widespread in the world as it is widely used in a lot of industries, its high water solubility make it as pollutant for seas and oceans due to oil production and exploration operations spills, BTEX compounds clssified as carcinogenic compounds.
biodegradation of BETX compounds was studied under normal conditions, but litle is known about its biodegradation under extrem conditions specially at high salinity and high pH, this due to inability of native microorganisms in these habitats to degrade it , so, it is important to make isolation of microorganism able to degrade BTEX and use it as a sole source of carbone and energy under these conditions.
There are three main targets for this study:
Frist; isolation and identification of bacterial strains able to degrade BETX under extreme condions (high salinity – high pH) from highly saline alkaline habitates.
Second; detection of catechol 2,3 dioxygenase enzyme which considered one of the important enzymes involved in BETX degradation.
Third; detecting, cloning and over expression of catechol 2,3 dioxygenase in these new isolates.
In the following results of this study:
1) Isolation of three isolates from high salinity and high pH sites, one was isolated from Ras Seder coastline in east Sini –Red sea, the other two isolates were from Abo Qir coastline Mediterranean Sea, these isolates were able to use BTEX as a sole source of carbon and energy.
2) Testing enzyme activity for these three isolates through tesing there ability to degrade BTEX and changing bacterial colonies to yellow colour by using catechol which refers to presence of catechol 2,3 dioxygenase enzyme which able to degrade benzene compounds.
3) Morphological and biochemical Identification of bacterial isolates which indicate that they follow Pseudomonas , then making 16S rRNA identification of isolates which were identified as Pseudomonas sp. HA10, Pseudomonas sp. HA12 and Pseudomonas sp. HA14.
4) Studing the releation between nucleotide sequence for 16S rRNA gene for each strain individually and nucleotide sequence for 16S rRNA for some strains which able to use aromatic componds, it was found that 16S rRNA nucleotide sequence for Pseudomonas sp. HA10 identical for 16S rRNA nucleotide sequence for strains of Pseudomonas alcaliphila strain L8, Pseudomonas sp. BC043 and Pseudomonas sp. p-wp0231 which aproved there ability to degrade MTBE,CAR and PAH respectively.
Also, 16S rRNA nuclotide sequence for Pseudomonas sp. HA12 identical for 16S rRNA nucleotide sequence for strains of Pseudomonas putida strain EC31, Pseudomonas putida strain CB2-1 and Pseudomonas sp. JA4 which approved there ability to degrade alkyl phenol polyethoxylate ,chlorobenzene and benzaldehyde respectively.
Also, 16S rRNA nuclotide sequence for Pseudomonas sp. HA14 identical for 16S rRNA nucleotide sequence for strains of Pseudomonas sp.PDI, Pseudomonas putida strain CB2-1 and Pseudomonas sp.PND-1 which aproved there ability to degrade phenol, chlorobenzene and phenol.
5) Testing the ability of three strains to grow on salinity range 0% to 12 % and high pH range between 7 – 11, it was found that all the three strains able to grow at NaCl concentrations range between 1.5% to 10%, and not able to grow at NaCl cocentration less than 1.5 or more than 10%. It was found that the optimum growth for Pseudomonas sp. HA10 at 7% NaCL concentration, while for Pseudomonas sp. HA12 was at 9% and for Pseudomonas sp. HA14 was at 8%.and also all these strains able to grow at high pH range from 8 to 11 but not at less than 8 or higher than 11, and optimum growth for three isolates were at pH 10, but for biodegradation ability at high pH it was found that only Pseudomonas sp. HA10 was able to degrde BETX at high pH and the optimum pH for degradation was 10 , but for Pseudomonas sp. HA12 and Pseudomonas sp. HA14 were able to degrade BTEX only at high NaCL concentration but not at high pH.
6) Catechole 2,3 dioxygenase isolation from isolated strains ,then its cloning in pGEM®-T Easy Vector , it was found that the three clones were able to degrade catechol and convert it to 2- hydroxyl muconic semialdehyde, then making plasmid isolation from these clones, and nucleotide sequence by using M13f and M13r primers.
7) After nucleotide sequence for catechol 2,3 dioxygenase obtained from the three isolates and comparing the published sequences with that for other strains which able to degrade the aromatic compunds it was found that neocleotide sequence for catechol 2,3 dioxygenase in Pseudomonas sp. HA10 similar to that found in Pseudomonas putida by 99% and to that found in Pseudomonas oryzihbitans by 95%, also for nuleotid sequence for catechol 2,3 dioxygenase gene in Pseudomonas sp. HA12 was similar to that found in Pseudomonas sp.S-47 by 99% and to that found in Pseudomonas putida by 95%, and also nuleotid sequence for catechol 2,3 dioxygenase gene in Pseudomonas sp. HA14 was similar to that found in Pseudomonas oryzihabitans by 99% and to that found in Pseudomonas sp. S-47 by 99%.