Glutathione Plays a Significant Role in the Growth, Oxidative Stress Response, and Sporulation in Myxococcus xanthus

By protecting the cells against oxidative and osmotic stress, glutathione (GSH) plays particularly important roles in bacteria. Glutathione is synthesized through two ATP-dependent reactions catalyzed by glutamate-cysteine ligase (Gcl) and glutathione synthetase (Gs). In addition, glutathione reductase (Gr) catalyzes the reduction of glutathione disulfide to its sulfhydryl form, GSH. In Myxococcus xanthus cells, the activities of Gcl, Gs, and Gr were found to be the highest during the stationary phase of growth and declined during starvation-induced development. In growth medium, compared with the wild-type strain, M. xanthus gcl mutant cells were characterized by a longer generation time and lower maximum cell density. During growth, the gcl mutant produced a browning substance in nutrient medium and the culture fluid inhibited horseradish peroxidase and thioredoxin reductase activities. In H₂O₂-supplemented medium, the gcl mutant was characterized by a marked retardation of growth and a longer generation time than the wild-type strain. Furthermore, the gcl mutant formed spores 2 days later than the wild-type strain, and at 11 days post-inoculation onto starvation medium, the yield of viable spores was approximately 1% that of the wild-type strain. These findings indicate that GSH plays an important role in the growth, adaptation to oxidative stress, and starvation-induced development of M. xanthus.