Amphibacillus xylanus is a recently identified bacterium which grows well under both aerobic and anaerobic conditions and may prove useful for biomass utilization. Amphibacillus xylanus, despite lacking a respiratory chain, consumes oxygen at a similar rate to Escherichia coli (130–140 μmol oxygen·min −1 ·g −1 dry cells at 37 °C), suggesting that it has an alternative system that uses a large amount of oxygen. Amphibacillus xylanus NADH oxidase (Nox) was previously reported to rapidly reduce molecular oxygen content in the presence of exogenously added free flavin. Here, we established a quantitative method for determining the intracellular concentrations of free flavins in A. xylanus , involving French pressure and ultrafiltration membranes. The intracellular concentrations of flavin adenine dinucleotide ( FAD ), flavin mononucleotide ( FMN ), and riboflavin were estimated to be approximately 8, 3, and 1 μ m , respectively. In the presence of FAD , the predominant free flavin species, two flavoproteins Nox (which binds FAD ) and NAD (P)H oxidoreductase (Npo, which binds FMN ), were identified as central free flavin‐associated enzymes in the oxygen metabolic pathway. Under 8 μ m free FAD , the catalytic efficiency ( k cat / K m ) of recombinant Nox and Npo for oxygen increased by approximately fivefold and ninefold, respectively. Nox and Npo levels were increased, and intracellular FAD formation was stimulated following exposure of A. xylanus to oxygen. This suggests that these two enzymes and free FAD contribute to effective oxygen detoxification and NAD (P) + regeneration to maintain redox balance during aerobic growth. Furthermore, A. xylanus required iron to grow aerobically. We also discuss the contribution of the free flavin‐associated system to the process of iron utilization.

No abstract

Reinforcement of the hydroperoxide-eliminating activity in the small and large intestines should prevent associated diseases. We previously isolated a lactic acid bacterium, Pediococcus pentosaceus Be1 that facilitates a 2-electron reduction of hydrogen peroxide to water. In this study, we successfully isolated an alternative lactic acid bacterium, Lactobacillus plantarum P1-2, that can efficiently reduce environmental alkyl hydroperoxides and fatty acid hydroperoxides to their corresponding hydroxyl derivatives through a 2-electron reduction. Each strain exhibited a wide concentration range with regard to the environmental reducing activity for each hydroperoxide. Given this, the two lactic acid bacteria were orally administered to an oxygen-sensitive short-lived nematode mutant, and this resulted in a significant expansion of its lifespan. This observation suggests that P. pentosaceus Be1 and L. plantarum P1-2 inhibit internal oxidative stress. To determine the specific organs involved in this response, we performed a similar experiment in rats, involving induced lipid peroxidation by iron-overloading. We observed that only L. plantarum P1-2 inhibited colonic mucosa lipid peroxidation in rats with induced oxidative stress. Citation: Watanabe A, Yamaguchi T, Murota K, Ishii N, Terao J, Okada S, et al. (2020) Isolation of lactic acid bacteria capable of reducing environmental alkyl and fatty acid hydroperoxides, and the effect of their oral administration on oxidative-stressed nematodes and rats. PLoS ONE 15(2): e0215113. https://doi.org/10.

No abstract

Free flavins accelerate release of ferrous iron from iron storage proteins by both free flavin-dependent and-independent ferric reductases in Escherichia coli