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Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky College of Medicine, MS415 Chandler Medical Center, Lexington, KY 40536-0298, USA
Correspondence
Brian Stevenson
brian.stevenson{at}uky.edu
The Lyme disease spirochaete, Borrelia burgdorferi, produces the LuxS enzyme both in vivo and in vitro; this enzyme catalyses the synthesis of homocysteine and 4,5-dihydroxy-2,3-pentanedione (DPD) from a by-product of methylation reactions. Unlike most bacteria, B. burgdorferi is unable to utilize homocysteine. However, DPD levels alter expression levels of a subset of B. burgdorferi proteins. The present studies demonstrate that a single B. burgdorferi operon encodes both of the enzymes responsible for synthesis of DPD, as well as the enzyme for production of the Lyme spirochaete's only activated-methyl donor and a probable phosphohydrolase. Evidence was found for only a single transcriptional promoter, located 5' of the first gene, which uses the housekeeping
70 subunit for RNA polymerase holoenzyme function. All four genes are co-expressed, and mRNA levels are growth-rate dependent, being produced during the exponential phase. Thus, high metabolic activity is accompanied by increased cellular levels of the only known borrelial methyl donor, enhanced detoxification of methylation by-products, and increased production of DPD. Therefore, production of DPD is directly correlated with cellular metabolism levels, and may thereby function as an extracellular and/or intracellular signal of bacterial health.
Present address: BioVitesse, West Lafayette, IN 47906, USA.
Present address: Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL 32610, USA.
A supplementary figure showing the results of Q-RT-PCR analysis of luxS transcription by wild-type (wt), rpoN and rpoS B. burgdorferi and two supplementary tables of raw data for the Q-RT-PCR are available with the online version of this paper.
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