title: High concentrations of intracellular Ap4A and/or Ap5A in developing Myxococcus xanthus cells inhibit sporulation.
abstract: Diadenosine polyphosphates (ApnA) are thought to act as signalling molecules regulating stress responses and biofilm formation in prokaryotes. However, ApnA function in Myxococcus xanthus remains unknown. Here, we investigated the role of ApnA in M. xanthus, using the wild-type and ApnA hydrolase (apaH) mutant strains exposed to various stress conditions. In both wild-type and apaH mutant cells cultured on starvation medium (CF agar), the levels of intracellular diadenosine tetraphosphate (Ap4A) and pentaphosphate (Ap5A) increased several fold during the first 16 h of development and decreased gradually thereafter. The levels of Ap4A and Ap5A in the apaH mutant were about 5- and 11-fold higher than those in the wild-type strain at 16 h, respectively. ApnA hydrolase activity of the wild-type strain increased 1.5-fold during the first 8 h of development, and it then gradually decreased. The apaH mutant formed spores 1-2 days after the wild-type strain did, and the yield of viable spores was 5.5 % of that in the wild-type strain 5 days after inoculation onto CF agar. These results suggest the possibility that high intracellular levels of Ap4A and/or Ap5A may inhibit M. xanthus sporulation at the early stage of development and that the bacteria reduce intracellular Ap4A and Ap5A accumulation through ApnA hydrolase activity.
authors.affiliation: Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kimura
authors.affiliation: Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Tanaka
authors.affiliation: Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
authors.forename: Katsuho
authors.initials: K
authors.lastname: Sasaki
authors.affiliation: Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Sasaki
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000235:genetics*; D000255:Adenosine Triphosphate / Q000378:metabolism; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D016941:Myxococcus xanthus / Q000378:metabolism*; D015398:Signal Transduction; D013171:Spores, Bacterial / Q000254:growth & development*; D013217:Starvation
chemical_list: D015226:Dinucleoside Phosphates; C012275:P(1),P(5)-di(adenosine-5'-)pentaphosphate; C020733:diadenosine tetraphosphate; D000255:Adenosine Triphosphate; D017766:Acid Anhydride Hydrolases; C075829:diadenosine polyphosphate hydrolase