title: An Essential Poison: Synthesis and Degradation of Cyclic Di-AMP in Bacillus subtilis.
abstract: Gram-positive bacteria synthesize the second messenger cyclic di-AMP (c-di-AMP) to control cell wall and potassium homeostasis and to secure the integrity of their DNA. In the firmicutes, c-di-AMP is essential for growth. The model organism Bacillus subtilis encodes three diadenylate cyclases and two potential phosphodiesterases to produce and degrade c-di-AMP, respectively. Among the three cyclases, CdaA is conserved in nearly all firmicutes, and this enzyme seems to be responsible for the c-di-AMP that is required for cell wall homeostasis. Here, we demonstrate that CdaA localizes to the membrane and forms a complex with the regulatory protein CdaR and the glucosamine-6-phosphate mutase GlmM. Interestingly, cdaA, cdaR, and glmM form a gene cluster that is conserved throughout the firmicutes. This conserved arrangement and the observed interaction between the three proteins suggest a functional relationship. Our data suggest that GlmM and GlmS are involved in the control of c-di-AMP synthesis. These enzymes convert glutamine and fructose-6-phosphate to glutamate and glucosamine-1-phosphate. c-di-AMP synthesis is enhanced if the cells are grown in the presence of glutamate compared to that in glutamine-grown cells. Thus, the quality of the nitrogen source is an important signal for c-di-AMP production. In the analysis of c-di-AMP-degrading phosphodiesterases, we observed that both phosphodiesterases, GdpP and PgpH (previously known as YqfF), contribute to the degradation of the second messenger. Accumulation of c-di-AMP in a gdpP pgpH double mutant is toxic for the cells, and the cells respond to this accumulation by inactivation of the diadenylate cyclase CdaA.
  
  
  OBJECTIVE
  Bacteria use second messengers for signal transduction. Cyclic di-AMP (c-di-AMP) is the only second messenger known so far that is essential for a large group of bacteria. We have studied the regulation of c-di-AMP synthesis and the role of the phosphodiesterases that degrade this second messenger. c-di-AMP synthesis strongly depends on the nitrogen source: glutamate-grown cells produce more c-di-AMP than glutamine-grown cells. The accumulation of c-di-AMP in a strain lacking both phosphodiesterases is toxic and results in inactivation of the diadenylate cyclase CdaA. Our results suggest that CdaA is the critical diadenylate cyclase that produces the c-di-AMP that is both essential and toxic upon accumulation.
authors.affiliation: Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Gundlach
authors.affiliation: Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany.
authors.forename: Felix M P
authors.initials: FM
authors.lastname: Mehne
authors.affiliation: Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Herzberg
authors.affiliation: Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Kampf
authors.affiliation: Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Valerius
authors.affiliation: Research Core Unit Metabolomics, Hanover Medical School, Hanover, Germany.
authors.forename: Volkhard
authors.initials: V
authors.lastname: Kaever
authors.affiliation: Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany jstuelk@gwdg.de.
authors.forename: Jörg
authors.initials: J
authors.lastname: Stülke
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015226:Dinucleoside Phosphates / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D009154:Mutation; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism*; D019761:Phosphorus-Oxygen Lyases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D015226:Dinucleoside Phosphates; C528998:cyclic diadenosine phosphate; D010727:Phosphoric Diester Hydrolases; D019761:Phosphorus-Oxygen Lyases; C528997:diadenylate cyclase, Bacillus subtilis