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Journal of Bacteriology, February 2009, p. 1293-1302, Vol. 191, No. 4
0021-9193/09/$08.00+0     doi:10.1128/JB.01170-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Growth Deficiencies of Neisseria meningitidis pfs and luxS Mutants Are Not Due to Inactivation of Quorum Sensing{triangledown}

Karin Heurlier,1,2* Agnès Vendeville,3 Nigel Halliday,1 Andrew Green,1,4 Klaus Winzer,1,5 Christoph M. Tang,3 and Kim R. Hardie1

Institute of Infection, Inflammation and Immunity, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, United Kingdom,1 Department of Food Sciences, University of Nottingham, Sutton Bonington LE12 5RD, United Kingdom,2 Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, United Kingdom,3 The Roslin Institute and Royal School of Veterinary Studies, Ogston Building, University of Edinburgh, Edinburgh EH9 3JF, United Kingdom,4 School of Health and Medicine, Division of Biomedical and Life Sciences, Lancaster University, Lancaster LA1 4YQ, United Kingdom5

Received 19 August 2008/ Accepted 2 December 2008

The activated methyl cycle (AMC) is a central metabolic pathway used to generate (and recycle) several important metabolites and enable methylation. Pfs and LuxS are considered integral components of this pathway because they convert S-adenosylhomocysteine (SAH) to S-ribosylhomocysteine (SRH) and S-ribosylhomocysteine to homocysteine (HCY), respectively. The latter reaction has a second function since it also generates the precursor of the quorum-sensing molecule autoinducer 2 (AI-2). By demonstrating that there was a complete lack of AI-2 production in pfs mutants of the causative agent of meningitis and septicemia, Neisseria meningitidis, we showed that the Pfs reaction is the sole intracellular source of the AI-2 signal. Analysis of lacZ reporters and real-time PCR experiments indicated that pfs is expressed constitutively from a promoter immediately upstream, and careful study of the pfs mutants revealed a growth defect that could not be attributed to a lack of AI-2. Metabolite profiling of the wild type and of a pfs mutant under various growth conditions revealed changes in the concentrations of several AMC metabolites, particularly SRH and SAH and under some conditions also HCY. Similar studies established that an N. meningitidis luxS mutant also has metabolite pool changes and growth defects in line with the function of LuxS downstream of Pfs in the AMC. Thus, the observed growth defect of N. meningitidis pfs and luxS mutants is not due to quorum sensing but is probably due to metabolic imbalance and, in the case of pfs inactivation, is most likely due to toxic accumulation of SAH.

* Corresponding author. Mailing address: Department of Food Sciences, University of Nottingham, Sutton Bonington LE12 5RD, United Kingdom. Phone: 44 (0) 115 9516197. Fax: 44 (0) 115 9516142. E-mail: Karin.heurlier{at}nottingham.ac.uk

{triangledown} Published ahead of print on 12 December 2008.

Journal of Bacteriology, February 2009, p. 1293-1302, Vol. 191, No. 4
0021-9193/09/$08.00+0     doi:10.1128/JB.01170-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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