Expression of SOD and production of reactive oxygen species in Acinetobacter calcoaceticus caused by hydrocarbon oxidation

Expression of antioxidant enzymes [superoxide dismutase (SOD) and catalase] and generation of reactive oxygen species (ROS) in the presence of various hydrocarbons were investigated in two strains of hydrocarbon-degrading microorganism Acinetobacter calcoaceticus isolated from water (VKPM B-10353) and bottom sediment (EMBM-06). Upon biotransformation of hydrocarbons by the studied strains, superoxide generation strengthening by bacterial cells and accumulation of peroxides in the cultivation medium were observed. The strongest superoxide anion radical generation occurred during the incubation of microorganisms with diesel fuel (increasing 12 times and 2 times), cyclohexane (1.8 times and 1.75 times), a mix of benzene and anthracene (4.4 times and 3.7 times), naphthalene (8 times and 1.9 times) and benz(a)pyrene (2 times and 2.3 times) in strains VKPM B-10353 and EMBM-06 respectively, and anthracene (2.8 times) in strain VKPM B-10353. The accumulation of peroxides in the medium took place upon biotransformation of diesel fuel by both strains. Activity of SOD increased considerably and activity of catalase decreased in cells in the medium with hydrocarbons. Decane and crude oil had the maximum impact on SOD expression. Decane increased SOD expression in strains VKPM B-10353 and EMBM-06 24.4 times and 28.5 times, respectively. Crude oil increased SOD expression in strain VKPM B-10353 19 times, and in strain EMBM-06 16 times. The authors assumed that increased ROS generation and oxidizing stress development in bacteria during the biotransformation of various hydrocarbons can have an adaptive character.