E. coli diversification within their ecological niches was studied phenotypically through phage typing. Three water sites which were ecologically variable (well, river and drainage) were selected for isolation of E. coli by multiple tube fermentation technique and identification through biolog system. Three isolates were designated as E. coli-EG1, E.coli-EG2 and E. coli-EG3 to represent their source from well, river and drainage, respectively. Spot test and plaque assay were adopted for discriminating among such isolates and showed sensitivity for E. coli-EG1 and E. coli-EG2, but quantitatively E. coli-EG1 exceeded E. coli-EG2 as, 105 and 103 PFUs respectively. The image processing and numerical analysis for plaque assay data revealed small variations in mean, median, standard deviation and number of pixels. The last was the most important as it indicated no far extent in sensitivity of E. coli-EG1as compared to E. coli-EG2. The differential behavior towards phage infection was attributed to mutational effect caused by environmental stress and exerted the role for the generation of new phenotypes which had fundamentally evolutionary impact. From our knowledge a first automated image processing method used for evaluation of plaques number based on scale and rotation invariant analysis of optical transforms was applied here.