The use of computerized television morphodensitometry in the study of microbial antagonism

Abstract

Computerized television morphodeusitometry has been applied for the first time to evaluate quantitatively and qualitatively the inhibitory effects associated with microbial antagonism. It is shown that the use of CTM for this purpose cart add to the existing knowledge about the inhibitory potentials of biologically active substances which microbial antagortists produce, in particular by demonstrating that when no growth of bacterial test cultures exposed to an antagonist is detectable visually there may still be some growth in the form of L transformation, and by enabling this growth to be quantified. Key Words: morphodensitomelry; image analysis; microbial antagonismTo date, systems for pattern recognition and image analysis have been used in microbiology very rarely and mostly in primitive routine studies (e.g., to follow the growth of yeasts or variations in bacterial cell numbers in a substrate [4,[7][8][9][10]. This is because a large gap exists between the potentials of morphodensitometric systems and their practical output. Yet computerized television morphodensitometry (CTM) --a method by which morphological characteristics of biological specimens can be reconstructed from their optical densities using digital image processing --not only expedites quantitative analyses but also yields important and qualitatively new information [2] that remains virtually inaccessible to visual observations and to conventional microbiological techniques (such as light or electron microscopy) because of the enormous natural variability of microbiological objects and of their morphological structures. Methods of determining microbial antagonistic activity that rely on the use of diffusion into agar [5] can provide only visual information about the actions of biologically active substances (BAS) produced by the microorganisms and do not permit a quantitative evaluation of cell death in the test cultures exposed to the antagonist: the visually observed growth retardation or cessation does not yet give an indication of the actual inhibitory antagonistic effect as no account is taken of bacterial L transformation and reversion. The use of ATB densitometers (Switzerland) to determine the sensitivity of enterobacteria to antibiotics [6] failed to provide data on morphological changes in bacterial populations and, moreover, a comparison with the traditional disk method showed significant differences between the results produced by these two methods.In view of the foregoing, we decided to adapt the method of CTM for quantitative evaluation of microbial antagonism, using model test cultures of Staphylococcus aureus and Escherichia coil