ISOLATION AND IDENTIFICATION OF PSEUDOMONAS PUTIDA AND STUDY ITS ABILITY TO DEGRADE HYDROCARBONS COMPOUNDS

number: 
1332
إنجليزية
Degree: 
Author: 
Haider Sadiq Abd Al-Hassan
Supervisor: 
Dr. Hameed M. Al-Dulaimi
year: 
2006

 

          Sixteen soil samples contaminated with different hydrocarbons were collected from seven locations in Baghdad governorate. From these samples there were 70 isolates were obtained and ten of them were subjected to morphological and physiological studies and biochemical tests. Five of them (Symboled H2, H3, H5, H6 and H9) were characterized as Pseudomonas putida.       The ability of local isolates of P. putida for biosurfactant production, hydrocarbons biodegradation and heavy metal resistance were studied. Results showed that  P. putida H6 was the best ,because of its high efficiency for biosurfactant production and lowering the surface tension of cell-free supernatants when it was grown in mineral salt medium containing crude oil , engine oil , kerosene , soyabeen oil and sunflower oil as  sole source for carbon and energy. It was also shown that this isolate was the efficient in biodegradation of aliphatic hydrocarbons (octane and decane), and aromatic hydrocarbons (Anthracene, cyclohexane, naphthalene, naphthol, benzene, phenol, salicylic acid, sodium benzoate, trans-1-2-diphenyl-ethylene, xylene). Further more P. putida H6 was able to resist heavy metals. It was found that this isolates was resist to cadmium, copper, iron, mercury and zinc.   Plasmid profile of P. putida H6 was studied through the extraction of plasmid DNA by salting-out procedure. Results of agarose gel electrophoresis showed that this isolate harboring two small plasmids that may be responsible for some of the biocharacteristics of this isolates. So, curing of plasmid DNA was achieved using ethidium bromide, then cured cells that lost the antibiotic resistance to carbencillin ,erythromycin ,penicillin and tetracycline were selected and used to study its ability in biosurfactant production, hydrocarbons biodegradation and heavy metal resistance. Result showed that this cured cells (Symboled P.putida H64) was still the efficient in biosurfactant production, and lowering surface tension in its cell-free supernatants. This result refers to biosurfactant trait was chromosomally encoded. It was also found that this cured cell was lost its ability in biodegradation of salicylic acid and xylene, which may be refers to plasmid origin of these traits, while it was still efficient in biodegradation of the other aliphatic and aromatic hydrocarbons.     In addition, cured cells of P. putida H64 were lost its ability in the resistance to cadmium and mercury, which may be also, refers that resistance traits are plasmidly encoded, while it was also still efficient to resist other heavy metals.