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  • (p)ppGpp, a Small Nucleotid...
    Oh, Young Taek; Lee, Kang-Mu; Bari, Wasimul; Raskin, David M.; Yoon, Sang Sun

    The Journal of biological chemistry, 05/2015, Letnik: 290, Številka: 21
    Journal Article

    When V. cholerae encounters nutritional stress, it activates (p)ppGpp-mediated stringent response. The genes relA and relV are involved in the production of (p)ppGpp, whereas the spoT gene encodes an enzyme that hydrolyzes it. Herein, we show that the bacterial capability to produce (p)ppGpp plays an essential role in glucose metabolism. The V. cholerae mutants defective in (p)ppGpp production (i.e. ΔrelAΔrelV and ΔrelAΔrelVΔspoT mutants) lost their viability because of uncontrolled production of organic acids, when grown with extra glucose. In contrast, the ΔrelAΔspoT mutant, a (p)ppGpp overproducer strain, exhibited better growth in the presence of the same glucose concentration. An RNA sequencing analysis demonstrated that transcriptions of genes consisting of an operon for acetoin biosynthesis were markedly elevated in N16961, a seventh pandemic O1 strain, but not in its (p)ppGpp0 mutant during glucose-stimulated growth. Transposon insertion in acetoin biosynthesis gene cluster resulted in glucose-induced loss of viability of the ΔrelAΔspoT mutant, further suggesting the crucial role of acetoin production in balanced growth under glucose-rich environments. Additional deletion of the aphA gene, encoding a negative regulator for acetoin production, failed to rescue the (p)ppGpp0 mutant from the defective glucose-mediated growth, suggesting that (p)ppGpp-mediated acetoin production occurs independent of the presence of AphA. Overall, our results reveal that (p)ppGpp, in addition to its well known role as a stringent response mediator, positively regulates acetoin production that contributes to the successful glucose metabolism and consequently the proliferation of V. cholerae cells under a glucose-rich environment, a condition that may mimic the human intestine. Background: Bacteria respond to nutrient starvation by (p)ppGpp that activates the stringent response. Results:V. cholerae mutants defective in (p)ppGpp production lost their viability during glucose-supplemented growth because of overproduction of organic acids. Conclusion: (p)ppGpp regulates energy metabolism, contributing to the successful proliferation of V. cholerae under glucose-rich environments. Significance: We report a previously unexplored role of (p)ppGpp in V. cholerae glucose metabolism.