H2O2, a potent oxidant, is an unavoidable by-product of the aerobic lifestyle, but has deleterious effects on cells. Micro-organisms grown under vigorously aerated conditions, e.g. fungi such as A. niger used to express recombinant proteins, may thus experience oxidative stress from reactive oxygen species (ROS). In the present study, we investigated the effects of H2O2 upon A.niger B1-D (an expression system for lysozyme). Our findings indicate that A. niger B1-D, can become adapted to H2O2. Pre-treatment of H2O2 at a non-lethal concentration (100 μM) in early exponential phase of A. niger B1-D prevented subsequent H2O2 killing at a lethal concentration (10mM). A number of antioxidant enzymes activities, CAT, GPx, GR, were induced by the pre-treatment, of which CAT activity was the most significant. The concentration of antioxidant GSH was also increased in ’adapted’ cultures, as was the oxidized form, GSSG, accompanied by a decrease of GSH/GSSG ratio. Also, both intracellular and extracelluar non-specific proteolytic activities increased in response to H2O2, resulting in a simultaneous decrease of intracellular protein concentration. In ’adapted’ cultures, the enhancement of antioxidant activities, enzymatic or non-enzymatic, helped the cells to detoxify H2O2 rapidly and completely; while the induction of proteolytic activities seemed to correlate to their tolerance to lethal levels of H2O2.
Full conference title:
158th Meeting of the Society of General Microbiology
- SGM 158th (2006)