title: A glutathione-dependent detoxification system is required for formaldehyde resistance and optimal survival of Neisseria meningitidis in biofilms.
abstract: OBJECTIVE
  The glutathione-dependent AdhC-EstD formaldehyde detoxification system is found in eukaryotes and prokaryotes. It is established that it confers protection against formaldehyde that is produced from environmental sources or methanol metabolism. Thus, its presence in the human host-adapted bacterial pathogen Neisseria meningitidis is intriguing. This work defined the biological function of this system in the meningococcus using phenotypic analyses of mutants linked to biochemical and structural characterization of purified enzymes.
  
  
  RESULTS
  We demonstrated that mutants in the adhC and/or estD were sensitive to killing by formaldehyde. Inactivation of adhC and/or estD also led to a loss of viability in biofilm communities, even in the absence of exogenous formaldehyde. Detailed biochemical and structural analyses of the esterase component demonstrated that S-formylglutathione was the only biologically relevant substrate for EstD. We further showed that an absolutely conserved cysteine residue was covalently modified by S-glutathionylation. This leads to inactivation of EstD.
  
  
  METHODS
  The results provide several conceptual innovations. They provide a new insight into formaldehyde detoxification in bacteria that do not generate formaldehyde during the catabolism of methanol. Our results also indicate that the conserved cysteine, found in all EstD enzymes from humans to microbes, is a site of enzyme regulation, probably via S-glutathionylation.
  
  
  CONCLUSIONS
  The adhc-estD system protects against formaldehyde produced during endogenous metabolism.
authors.affiliation: Australian Centre for Infectious Disease Research, School of Chemistry and Molecular Biosciences, Faculty of Science, The University of Queensland, St. Lucia, Australia.
authors.forename: Nathan H
authors.initials: NH
authors.lastname: Chen
authors.forename: Rafael M
authors.initials: RM
authors.lastname: Couñago
authors.forename: Karrera Y
authors.initials: KY
authors.lastname: Djoko
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jennings
authors.forename: Michael A
authors.initials: MA
authors.lastname: Apicella
authors.forename: Bostjan
authors.initials: B
authors.lastname: Kobe
authors.forename: Alastair G
authors.initials: AG
authors.lastname: McEwan
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000378:metabolism*; D018441:Biofilms / Q000187:drug effects*; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D005557:Formaldehyde / Q000494:pharmacology*; D009345:Neisseria meningitidis / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013869:Thiolester Hydrolases / Q000378:metabolism*
chemical_list: D005557:Formaldehyde; C020145:formaldehyde dehydrogenase (glutathione); D000445:Aldehyde Oxidoreductases; D013869:Thiolester Hydrolases