title: NO-induced biofilm dispersion in Pseudomonas aeruginosa is mediated by an MHYT domain-coupled phosphodiesterase.
abstract: Dispersion is a process used by bacteria to successfully transit from a biofilm to a planktonic growth state and to spawn novel communities in new locales. Alterations in bis-(3'-5')-cyclic dimeric GMP (c-di-GMP) levels have been shown to be associated with biofilm dispersal in a number of different bacteria. The signaling molecule nitric oxide (NO) is known to induce biofilm dispersion through stimulation of c-di-GMP-degrading phosphodiesterase (PDE) activity. However, no c-di-GMP modulating enzyme directly involved in NO-induced dispersion has yet been described in the opportunistic pathogen Pseudomonas aeruginosa. Here, we characterized MucR (PA1727) and NbdA (PA3311, NO-induced biofilm dispersion locus A), two membrane-bound proteins with identical domain organization consisting of MHYT-GGDEF-EAL, with respect to their role in NO-induced dispersion. Inactivation of mucR impaired biofilm dispersion in response to NO and glutamate, whereas inactivation of nbdA only impaired biofilm dispersion upon exposure to NO. A specific role of NbdA in NO-induced dispersion was supported by increased PDE activity, resulting in decreased c-di-GMP levels in biofilms expressing nbdA upon exposure to NO, a response that was absent in the ΔnbdA strain. Moreover, increased PDE activity was mainly due to a transcriptional activation of nbdA upon addition of NO. Biochemical analyses of recombinant protein variants lacking the membrane-anchored MHYT domain support NbdA being an active PDE. In contrast, MucR displayed both diguanylate cyclase and PDE activity in vitro, which seemed regulated in a growth-dependent manner in vivo. This is the first description of a PDE specifically involved in NO-induced biofilm dispersion in P. aeruginosa.
authors.affiliation: Department of Biological Sciences, Binghamton University, Binghamton, New York, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.forename: Sabrina
authors.initials: S
authors.lastname: Heine
authors.forename: Michael
authors.initials: M
authors.lastname: Entian
authors.forename: Karin
authors.initials: K
authors.lastname: Sauer
authors.forename: Nicole
authors.initials: N
authors.lastname: Frankenberg-Dinkel
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects* / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000494:pharmacology*; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D009569:Nitric Oxide; D010727:Phosphoric Diester Hydrolases