5148
Eman Ibrahim Farag
S t u d i e s o n t h e P r o d u c t i o n o f A n t i m i c r o b i a l A g e n t s f r o m S o m e S o i l M i c r o o r g a n i s m s A g a i n s t B a c t e r i a l P a t h o g e n s .
pathogenic, bacteria,currently directed
Rapidly emerging strains of bacteria resistant to most advanced antibiotics have become issues of very important public health concern. Research currently directed towards bacteria presents a vast potential for new compounds that could be able to safely and effectively target resistant species. In this regard, three bacterial strains isolated from the different locations in agricultural Egyptian soils were selected and assessed for antimicrobial agents production and activity against a wide range of bacteria including clinical strains, plant pathogenic bacteria, yeast and plant pathogenic fungi. The ethyl acetate extracts of the selected bacterial isolates showed activities against the all tested pathogenic bacteria and fungi while differ between them. Inhibition zones were found to range between 16.9-33 mm diameters at a concentration of 200 μg ml-1. The minimum inhibitory concentrations (MICs) of the crude extracts ranged from 0.0625μg/ml to 0.5μg/ml and it was noticed that the extracts are more active against Gram negative bacteria than Gram positive ones. For yeast and filamentous fungi, isolate SOF12 showed highest activityagainst Fusarium oxysporum with MIC of 0.0625 μg/ml, while isolate AMF11 has low activity against fusarium solani with MIC of 0.5. The isolate SMF4 was moderate activity against all the yeast and filamentous fungi tested. Based on it’s morphological and microscopy characteristics as well as 16S rRNA sequence analysis, the three isolates designated as SOF12, AMF11 and SMF4 were identified as Bacillus megaterium QST3.7, Bacillus licheniformis DV7 and Bacillus subtilis CHB1-3, respectively. To study the effect of some growth factors on the production of antagonistic bacterial metabolites against selected human and plant pathogenic bacteria; plant pathogenic fungi and yeasts. The results showed that the antimicrobial activity of the metabolites increased generally from zero to 54 hours of incubation, The optimum temperature for maximum activity by Bacillus megaterium and Bacillus licheniformis was recorded at 30°C while Bacillus subtilis at 25°C. The optimum pH for Bacillus megaterium and Bacillus licheniformis was 7, whereas Bacillus subtilis was at pH 8. The best carbon source for Bacillus megaterium was starch, while with Bacillus licheniformis, starch and glycerol were recorded as the best c-source but with Bacillus subtilis glycerol was the best. The asparagine was observed as the best additional nitrogen source for all the strains. The highest number of generation was recorded by B. megaterium and the lowest value was recorded by B. licheniformis. The pure fractions obtained from B. megaterium were identified by NMR spectroscopy (1H NMR and 13C NMR) along with data base searches (AntiBase, DNP etc). The B. megaterium yielded two pure compounds that were identified as3-(methyl amino) phenol and 1-methyl-1H-indol-5-ol.
2016
Ph.d
Minufyea
Science