الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The development of successful biological control agent , for a particular disease involves selection of a suitable bio-antagonist , followed by the formulation of an affective strategy of application , including both timing and mode of application
. Microorganisms that can grow in the rhizosphere are ideal for use as biocontrol agent since ; the thizosphere provides the front line defense for roots against pathogen
In this study , a total of 486 bacterial isolates were isolated from different potato plantation areas infected with Erwinia-carotovara ssp- Soil were collected from three govermorates ; Alexandria , El-Behera and El-Gharbia . They were tasted for their ability to produce antibacterial agent against the indicator bacterium Erwinia carotovora ssp. The casual pathogen of soft rot disease on potato Eight isolates proved to produce antagonestic substances against the indicator bacterium E.c. ssp cartotovara , for of them were ,more potent than others, with the ability to produce antigonistic substance extracelluary..
Characterization of the antagonistic substaance produced by the four isolates revealed that, three of them( BI, B4 and B15_ are non heat labile and protease sensitive ,and showed positive inhibitory effect in the presence of Fe CI3 . These three criteria indicated that , the previous isolates are a bacteriocin producer. The forth isolate ( S6) showed negative inhibitory effect in the presence of Fe CI3 , this criterion stated that isolate (s6) is a siderophor producer. However isolate (BI) was mainly selected from the previous three bacteriocin producers , because it was more potent against E. c. var. carotovora compared to the other two.
Optimizing bacteriiocine and siderophore production activity revealed that. Optimum Production / activity can be obtained after 48 hours incubation period in Bpy medium at pH 7 ,where the medium was supplemented with 2% glucose , and theproducer isolates grew at 30 o C .The bacteriocin producer was defined as the gram positive bacteium Bacillus cereus according to morophological and stines examination , and key biochemical tests, and results of api- 5OCH and api – 20 E kits . The siderophore producers was defined as the Gram negative bacterium Pseudomonas flutescnse according to morophological and stains examination , key biochemical tests , and results of api – 20E kit
For isolation and purification of bacteriocin produced by Bacillus , the bacterial cells were grown in BPYG broth medium 30 o C for 48 hours . The culture was centrifuged at 4025 xg for 10 min at 4 o C. The crude supermalant was precipitated with ammonium sulphate gradually up to 80% saturation, and then dialyzed against 25 mM choice was photosphate buffer ( PH7), and finally concentratef using Amicon filter. Consequently the choice was made on 60% ammonium sulfate saturation as the highest concentration at which the experiments will be carried out.
For isolation and purification of siderophore produced by pseudomonas fluorescens, the bacterial cells were growing in BPYG broth medium at 30 o C for 48 hours . The culture was centrifuged at 4025xg for 10 min at 4 o C. The crude supernatant was precipitated with acetone followed by affinity chromatography . The results showed two.