Citation

Gundlach J, Mehne FM, Herzberg C, Kampf J, Valerius O, Kaever V, Stülke J. J. Bacteriol. 2015; 197(20): 3265-3274.

Affiliation

Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Germany. jstuelk@gwdg.de.

Copyright

(Copyright © 2015, American Society for Microbiology)

DOI

10.1128/JB.00564-15

PMID

26240071

Abstract

Gram-positive bacteria synthesize the second messenger cyclic 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 that it 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 suggests a functional relation. 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 as compared to 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 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. IMPORTANCE: Bacteria use second messengers for signal transduction. Cyclic di-AMP is the only second messenger that is essential for a large group of bacteria known so far. We have studied the regulation of c-di-AMP synthesis and the role of the phosphodiesterases that degrade the second messenger. C-di-AMP synthesis strongly depends on the nitrogen source: glutamate-grown cell 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.

Language: en