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Growth-Phase-Related Changes in Reactive Oxygen Species Generation as a Cold Stress Response in Antarctic Penicillium Strains

ABSTRACT The Free Radical/Oxidative Stress Theory of Aging postulated that the accumulation of damage caused by reactive oxygen species (ROS) was the underlying mechanism by which organisms age. Our previous studies reported that the growth at low temperature caused oxidative stress events in Antarctic strains, including enhanced ROS generation. However, there is no data about age-related differences in cold stress-induced ROS accumulation in microorganisms living permanently in cold environments. The aim of the present paper was to evaluate the growth-phase-related changes in ROS level in two Antarctic strains belonging to different thermal classes, psychrotolerant (Penicillium olsonii p14) and mesophilic (Penicillium waksmanii m12) and the role of cold adaptation in this process. Intact cells and mitochondrial fractions from the middle exponential phase or stationary phase at optimal temperature were exposure to temperature of 6°C and 15°C, respectively. The results demonstrated that the temperature downshift led to a significant induction in the superoxide and H2O2 level in a dose- and growth-phase-dependent manner. Additionally, cold-stress response is not dependent on cold-adaptation of the model strains.