Role of Antioxidant Enzymes in Bacterial Resistance to Organic Acids

Abstract

Growth in aerobic environments has been shown to generate reactive oxygen species (ROS) and to cause oxidative stress in most organisms. Antioxidant enzymes (i.e., superoxide dismutases and hydroperoxidases) and DNA repair mechanisms provide protection against ROS. Acid stress has been shown to be associated with the induction of Mn superoxide dismutase (MnSOD) in Lactococcus lactis and Staphylococcus aureus. However, the relationship between acid stress and oxidative stress is not well understood. In the present study, we showed that mutations in the gene coding for MnSOD (sodA) increased the toxicity of lactic acid at pH 3.5 in Streptococcus thermophilus. The inclusion of the iron chelators 2,2-dipyridyl (DIP), diethienetriamine-pentaacetic acid (DTPA), and O-phenanthroline (O-Phe) provided partial protection against 330 mM lactic acid at pH 3.5. The results suggested that acid stress triggers an iron-mediated oxidative stress that can be ameliorated by MnSOD and iron chelators. These findings were further validated in Escherichia coli strains lacking both MnSOD and iron SOD (FeSOD) but expressing a heterologous MnSOD from S. thermophilus. We also found that, in E. coli, FeSOD did not provide the same protection afforded by MnSOD and that hydroperoxidases are equally important in protecting the cells against acid stress. These findings may explain the ability of some microorganisms to survive better in acidified environments, as in acid foods, during fermentation and accumulation of lactic acid or during passage through the low pH of the stomach.

Arginine Deiminase in Staphylococcus epidermidis Functions To Augment Biofilm Maturation through pH Homeostasis

“…In fact, earlier studies showed a direct link between acid stress and oxidative stress, as S. aureus defective in sodA is more susceptible to severe acid stress (75). Similarly, more recent studies in S. thermophilus found that the cytotoxic effects of both acid stress and oxidative stress were very similar, as acid stress induced generation of oxygen radicals, stimulating Fenton chemistry and subsequent OH ⅐ formation (51). Furthermore, those investigators found that manganese-dependent superoxide dismutase and, predictably, other antioxidant enzymes protected the cell against the deleterious effects of acid stress via reduction of superoxide radicals.…”

“…Recent studies of Streptococcus thermophilus found that manganese-containing superoxide dismutase (MnSOD) was required for growth and survival in media acidified to pH 3.5 by lactic acid (51). Furthermore, chelation of free intracellular soluble iron partially rescued pH-mediated death in an MnSOD mutant, suggesting that lactic acid dissociates protein-iron complexes, facilitating hydroxyl radical formation via Fenton chemistry (51-54).…”

Toxicity and efficiency study of plant extracts-based bleaching agents

“…These data suggest that the EBA acid stress generated in the human cells is similar to that reported for lactic acid. When exposed to the organic acids, the cells produced the hydroxyl radical via the Fenton/Haber-Weiss reactions [32][33][34], through a reaction of the Fe 3+ -acid complex [30], where the hydrogen peroxide was generated by cellular respiration. The possible bleaching effect of this Bintrinsicĥ ydroxyl radical might lead to a lower but significant bleaching effect (Fig.…”

Meta-Analysis and Functional Validation of Nutritional Requirements of Solventogenic Clostridia Growing under Butanol Stress Conditions and Coutilization ofd-Glucose andd-Xylose

“…Also, in preliminary chemostat pulse-and-shift experiments, we determined the nutritional requirement of the cells for bioavailable iron and lipids (data not shown). Therefore, the chemical siderophore EDTA (0.1 mM) was added to the medium to guarantee iron bioavailability and also to protect the cells from oxidative stress (13). The final pulse-shift experiment demonstrated that growth of strain SA-1/ATCC 35702 was limited in yeast extract, trace elements, MgSO 4 , and Tween 80 (Fig.…”