التفكك الحياتي لمبيدي الملاثيون والدورسبان باستخدام مزارع احاديه وخليطه من البكتيريا == Biodegradation of Malathion And Dursban By Mono And Mixed Bacterial Cultures
Author name:
فائزة كاظم عمران
Supervisor name:
عادل مشعان ربيع
General topic:
Biology
Specific topic:
Environment
Degree:
Doctorate
University:
University of Baghdad
Language:
English
University location:
Baghdad
First pages:
24T2697 - p.pdf
Abstract:
عزلت 45 عزلة بكتيرية محليه من مجموع 30 نموذج تربه ملوثة بالمبيدات والتي جمعت خلال فترات زمنيه مختلفة ومن مناطق مختلفه في بغداد. اختبرت قابلية العزلات البكتيريه على تفكيك مبيدي الملاثيون والدورسبان. اجريت غربلة اولية وثانوية باستخدام وسط الاملاح المعدنية ا | Forty five local bacterial isolates were isolated from thirty different soil sample contaminated with pesticide, These samples were collected from different Baghdad regions at different periods. The bacterial isolates were tested for their ability to biodegrade certain pesticides (Malathion and Dursban). Primary and secondary screenings were carried out using solid Mineral Salts Medium (MSM) and Liquid (MSM) with 100 ppm Malathion and Dursban at 37 0C, pH 7. Twenty seven isolates resistant to Malathion and Dursban were isolated. Out of 27 bacterial isolates from different locations in Baghdad. Results from primary screening showed that the 10 isolates had good growth, 5 isolates gave moderate growth, 12 showed weak growth and only 9 isolates failed to show any growth.According to current results, 10 bacterial isolates were tested for their ability to biodegradation of Malathion and Dursban in liquid medium, However, secondary screenings results by using minimal inhibition concentration(MIC) revealed that only four bacterial isolates had the highest ability to degrade Malathion and Dursban and subsequently were identified as Pseudomonas putida, Esherichia coli, Escherichia hermanii and Staphylococcus vitulinus by Vitek compact system respectively.The optimum conditions (incubation period, pH, temperature) for growth and biodegradation of Malathion and Dursban were examined. The obtained results indicated that the best incubation period was after 7 days, pH =6 and favorite temperature was 350C.Measurement physicochemical properties for soil pH, temperature (C°), electrical conductivity EC (µs/cm) for both Dursban and Malathion concentrations(ppm) collected from six different locations within Baghdad city. Biodegradation of Malathion and Dursban in soil inoculated with different bacterial mono - cultures and mixed - cultures were investigated. soil pH, temperature, electrical conductivity, cations and anions, on the population of native Malathion - Dursban tolerant bacteria in the cultivated soils of six sites. The result showed that soil physical properties like temperature and electrical conductivity affect significantly to native Malathion - Dursban tolerant bacterial density. Similarly, the soil chemical properties like pH, cations and anions had more effect on the abundance of Malathion - Dursban tolerant bacteria in the soil. However, the impact of soil organic carbon, organic nitrogen and available phosphorus was very significant. The results of the present study can be utilized for the development of effective bioremediation process for pesticide - contaminated soil. Under optimal conditions, Malathion and Dursban degradation was measured by using GC - MS analysis. The results revealed that Pseudomonas putida was the best isolate for degrading Dursban by monoculture isolate (47.18%) , while mixed culture(P.putida and S.vitulinus) was the best in degrading Malathion and Dursban that gave 90.84% and 81.055% respectively. Results also indicated that the number of byproducts produced by mono and mixed culture of Malathion and Dursban biodegradation. Whereas the results obtained from GC/Ms analysis revealed that not detected of toxic byproduct Malathion and Dursban degradation by Pseudomonas putida and Staphylococcus vitulins respectively.Moreover, under natural conditions.The study tested the ability of selected bacterial isolates (P. putida and S. vitulins) in biodegradation of Malathion and Dursban, the results showed slower biodegradation by selected bacterial isolates compared with laboratory conditions but study showed a intermediet product like phenol, diethyl phosphorothioate and oxon.The GC - MS results showed that the number of metabolic intermediates formed during the degradation of Malathion by bacterial mixed - culture were relatively higher in number than by bacterial mono - culture.The mass spectra of malathion containing samples treated with bacterial mono and mixed culture showed no any known toxic intermediates. The result indicated that the two main degradation products resulted from bacterial degradation, namely malathion monocarboxylic (MMA) and malathion dicarboxylic acid (MDA), the first one may convert into the latter over time. Some other degradation products may occur such as ethyl hydrogen fumarate (EHF) but in negligible amount.The result indicated that the main degradation products resulted from bacterial degradation of dursban is trichloropyridinol(TCP) and then de - chlorinated into 2 - pyridinol.The mass spectra results obtained in this study showed that the dursban was degraded to many metabolites.The results suggested that the bacterial isolates were not forming any toxic intermediates but no any intermediate was identified till R.T. 22 minutes. This indicated that dursban is probably completely metabolized by the isolates into smaller intermediatesThe isolate Pseudomonas putida isolated from soil contaminated with pesticides was identified genotypic tests. Molecular typing was performed by RAPD - PCR and comparison of the results to other Pseudomonas isolates. The result shows that genotyping differences between isolates and found the convergent percent biodegradation between this isolates of both selected pesticide, although from these differences, there was no more effect to biodegradation, which means that the biodegradation of Malathion and Dursban not related to genotype
