Although the starting concentration (“”dilution = 1″”) is close to the transmittance detection limit (95%), even a further 1000-fold dilution of this initial sample generated measurable mTOR inhibitor Thermal signal. This confirms recently reviewed findings of the microcalorimetric high sensitivity, far beyond that of turbidity measurements LY3023414 [12]. The following growth pattern is observed: the time lag and extension of the thermal signal
increase with increasing dilution. In the 1/1000 dilution case, sample growth is not completed within the chosen 20 hours experiment time limit. Figure 3 Variability test starting at room temperature ( freshly prepared samples ). Thermal signals of serial dilutions, 1/10, 1/100, 1/1000, of samples of T600~95% incubated at a temperature of 37°C. Signals generated by bacterial populations of increasing dilution show decreasing signal height and longer time to signal appearance. Variability with temperature at CHIR-99021 ic50 a
fixed transmittance is shown in Figure 4. Thermal signal is obtained faster, with slightly higher intensity with increasing of the growth (working) temperature. This follows the expected trend of growth rate increase with temperature. Figure 4 Variability test starting at low temperature ( samples kept in cold storage experiments). Thermal signal of a series of samples of the same transmittance (T600 = 90.1%) incubated at different temperatures: 33, 35 and 36°C. Thermal signal is obtained faster and is generally of higher Palmatine intensity with increasing temperature. Sources of signal perturbation The productive use of this method for the study of bacterial population dynamics entails the determination of the following important factors that might contribute to errors in generating data: 1. Sample preparation – we have encountered this error in experiments on freshly prepared samples. Storing the samples at low temperatures eliminates this error by using aliquots of the same bacterial preparation (as described in Methods). In this case one potential issue
was the viability of the bacterial samples stored at low temperature for a considerable amount of time (up to four days). We designed an experiment to test the lack of bacterial metabolic activity at low temperatures (Figure 5). One may notice that there is no sizable thermal activity of the bacterial population isothermally kept at a 4°C for 20 hours. However, the bacterial population is viable, as evidenced by its thermal activity at 37°C Subsequent recordings using samples kept at low temperature for up to 4 days provided similar signals. 2. The response of the microcalorimeter to perturbations produced by sample loading. All experiments are affected by perturbations during sample loading that potentially can mask early stage bacterial growth.