ABSTRACT
PM experiments are conducted in a specially designed incubator, the Omnilog, designed to hold fi fty 96-well plates and equipped with a CCD camera. The plates are incubated at the desired temperature, which can be set between 25 ° C and 45 ° C, and for a time period usually between 24 and 48 hr. Cell respiration leads to reduction of the tetrazolium dye that results in blue color. The intensity of the color, which is not only a direct measure of respiration, but also a good indirect measure of growth, is recorded for each well every 15 min by the CCD camera. The data are analyzed by the PM software and provide a quantitative analysis of respiration in each well of the plates. The software also plots the kinetic data of color formation in arbitrary units against time for each well and assigns an artifi cial color under the area of the curve. When two strains are analyzed simultaneously, red is used to signify the reference strain, and green indicates the strain that is being compared. Data from the two strains are shown by graphical overlays of the two plots. For example, when similar growth is observed for a mutant strain and its isogenic parent strain (the reference strain), the overlaid plot is yellow. If there is growth of the parent strain, but not the mutant under a given condition, the plot for that well is red, and, conversely, if the mutant grows, but not the parent strain, the plot is green.
