Determination of mean growth parameters of bacterial colonies immobilized in gelatin gel using a laser gel-cassette scanner

The potential of a laser gel-cassette scanner (LGS) for rapid, quantitative measurement of the effect of environmental factors such as pH, temperature and humectants on the lag and doubling times of microorganisms is explored. The quantitative relationships between the laser light scattering intensity and colony radius, mean lag time and doubling time are analysed and a measurement protocol is formulated and tested using the specific example of the effect of increasing salt concentration of the lag and doubling times of Salmonella typhimurium LT2. It is concluded that the LGS is a potentially valuable tool for the rapid determination of relative lag and doubling times, but that, because of the need for extensive calibration, it is not capable, at least in its present form, of reliably determining absolute values of lag and doubling times without at least one independent viable count measurement.