DETERMINING SPECIFIC GROWTH-RATES IN DIFFERENT REGIONS OF SALMONELLA-TYPHIMURIUM COLONIES

Computer-aided image analysis (IA) techniques were used to determine s pecific growth rates (mu) in different regions of Salmonella typhimuri um colonies grown on solid medium at 30 degrees C. Captured transmissi on images were converted to optical density values, allowing calculati on of mu. Data show that growth was exponential throughout the colony during the period studied (between 13 and 21 h after inoculation), but that mu varied from 0.69 to 0.37 h(-1) at the periphery and centre, r espectively. Results demonstrate regional variation in mu values withi n colonies, and support conceptual models of colony development. The t echnique described illustrates that kinetic growth data can be derived within bacterial colonies, and this may lead towards an improved unde rstanding of the growth dynamics of these structures.