Fig. 1

Temperature changes. The temperature of the medium in a 15-mL polypropylene conical tube was measured for 30 min using a digital thermometer. The tube with 500 µL of medium was transferred into a CO₂ incubator set at 41 °C for 20 min for heat stimulation, and then placed back into a CO₂ incubator set at 32 °C for another 10 min. The temperature within the medium was over 40 °C at 15 min, and immediately dropped in 10 min after the heat stimulus. This experiment was repeated 3 times, and values represent the means and standard deviations