Abstract
Abstract
Myxococcus xanthus synthesizes polyphosphates (polyPs) with polyphosphate kinase 1 (Ppk1) and degrades short- and long-chain polyPs with the exopolyphosphatases, Ppx1 and Ppx2, respectively. M. xanthus also expresses polyP:AMP phosphotransferase (Pap) which generates ADP from polyPs and AMP. M. xanthus synthesized polyPs during the stationary phase; the ppk1 mutant showed no difference in growth during the exponential growth phase but died earlier than the wild-type and ppx2 mutant after the stationary phase. In addition, M. xanthus cells cultured in phosphate-starved medium, 0.07 mM H2O2-supplemented medium, or nutrient-deficient medium (CF medium) increased the intracellular polyP levels by six- to eight-fold after 6 h of incubation. However, the growth of ppk1 and ppx2 mutants in phosphate-starved medium and 0.07 mM H2O2 supplemented medium was not significantly different from that of wild-type strains, nor was there a significant difference in fruiting body formation and sporulation on CF medium. The adenylate energy charge (AEC) values of the wild-type strain and the ppk1, ppx2, and pap mutant strains at the exponential growth phase were approximately 0.80. The AEC of the wild-type strain did not change until day 3 of development, whereas the AEC values of the ppk1 and pap mutant strains decreased to 0.77 due to an increase in AMP and a decrease in ADP. Spores of ppk1 and pap mutants in the nutrient medium germinated later than those of the wild-type strain. These results suggested that polyPs produced during development may play an important role in cellular energy homeostasis by being used to convert AMP to ADP via Pap.
Publisher
Research Square Platform LLC