الفهرس 
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Abstract
◄ Pesticides used for agricultural purposes as well as for non-agricultural purposes are considered one of the toxic chemicals. The use of agricultural pesticides has led to extensive pollution and destruction of biodiversity and eco-system therefore the increased use of pesticides in agriculture and household activities to combat insects led to severe pollution to the environment.
◄ Microorganisms, which were included are involved in water treatment contaminated with agricultural pesticides where they can degrade most of the pesticides biotically.
◄ The aim of this work was to investigate the ability of various bacterial isolates that are tolerant to different concentrations of atrazine (herbicide of triazine group), diazinon (insecticide of organophosphorus group ) and oxamyl (nematicide of carbamate group) in addition to their abilities to remove pesticides from contaminated water .
◄ Results obtained from this study can be summarized in the following points:
1 - Three types of bacterial isolates were isolated from agricultural drainage water in Fayoum governorate-Egypt. After identifying these strains by using 16SrDNA, they were Ochrobactrum oryzae, which tolerated high concentrations of atrazine reached 1000ppm, and Pseudomonas aeruginosa, which tolerated high concentrations of diazinon reached to 1000ppm and Enterobacter ludwigii which also resisted high concentrations of oxamyl reached 400ppm.
2 - Growth of the three bacterial strains was estimated in terms of protein content and optical density.
3 - All the bacterial strains have been grown in minimum salt medium (MSM) in absence of source of carbon and in presence of the pesticide as a sole carbon source.
4 - Different concentrations of each pesticide were used to show the effect of different concentrations of pesticide on growth measurements. These studies showed that growth of Ochrobactrum oryzae on atrazine, Pseudomonas aeruginosa on diazinon and Enterobacter ludwigii on oxamyl as a sole carbon source in MSM was on top at 400ppm, 500ppm, 200ppm, respectively where it was getting the highest OD and the highest protein content at these concentrations.
5 - After knowing the ideal concentration for growth of each bacterial isolate, effect of pH ( 5 , 7 and 9) and temperature (20 , 30, 37˚ C) on the growth rate and bioremoval rate for each pesticide were studied where:
a - Growth of O. oryezae on atrazine was as high as possible at pH tended to alkaline side (pH = 9) where the optical density was 0.68 and protein content 252.3 mg / l after ten days of incubation. Growth of P.aeruginosa on diazinon was as high as possible in neutral medium (pH = 7) where the optical density was 1.147 and the protein content was 328.5 mg / l after 14 days of incubation. Growth of E. ludwigii on oxamyl was the highest in neutral medium (pH = 7) where it was of optical density 0.376 and protein content 60 mg / l . b - Growth of the O.oryzae on atrazine was as high as possible at temperature 30˚C where optical density was 0.707 and protein content 220 mg / l after 10 days of incubation, growth of P.aeruginosa on diazinon was as high as possible at a temperature of 30˚ C where optical density was 1.05 and protein content was 348 mg / l after 14 days of incubation , and the growth of E. ludwigii on oxamyl was as high as possible at a temperature of 37° C where optical density was 0.396 and protein content was 55.8 mg /l after 6 days of incubation.
6- GC analysis , which was used to measure the residues of atrazine and diazinon showed that Ochrobactrum oryzae strain had diverse ability to degrade atrazine at different temperatures and pH with ratio of 83.5 % , 72.3 % , 16.2 % at pH 9 , 7, and 5, respectively and 59.3 % , 67.4 % , 20.1 % at temperatures 20 , 30 and 37˚C, respectively. GC analysis also showed the diverse ability of Pseudomonas aeruginosa to degrade diazinon at different temperatures and pH with ratio of 31.2%, 83.6 %, 81.4 % at pH 5, 7. And 9, respectively and 82.32 %, 83.52 %, 59.8 % at temperatures 20, 30 and 37°C, respectively.
7- HPLC analysis used to measure the residues of oxamyl showed the diverse ability of Enterobacter ludwigii to degrade oxamyl at different temperatures and pH with the ratio of 16.5 , 77.7, 0.45 % at pH 5 , 7, and 9, respectively and 42 , 73.1 , 77.4 % at temperatures 20 , 30, and 37 ° C respectively..
- The general conclusion from this study was that bacteria certainly represent a great and attractive hope for treatment of contaminated water from agricultural pesticides. Because being cheap and easy to grow in the laboratory, they play an important role in solving one of the biggest environmental problems in the world.