6533b7d6fe1ef96bd1266659

RESEARCH PRODUCT

Inducible metabolism of phenolic acids in Pediococcus pentosaceus is encoded by an autoregulated operon which involves a new class of negative transcriptional regulator.

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ABSTRACTPediococcus pentosaceusdisplays a substrate-inducible phenolic acid decarboxylase (PAD) activity onp-coumaric acid. Based on DNA sequence homologies between the three PADs previously cloned, a DNA probe of theLactobacillus plantarum pdcgene was used to screen aP. pentosaceusgenomic library in order to clone the corresponding gene of this bacteria. One clone detected with this probe displayed a low PAD activity. Subcloning of this plasmid insertion allowed us to determine the part of the insert which contains a 534-bp open reading frame (ORF) coding for a 178-amino-acid protein presenting 81.5% of identity withL. plantarumPDC enzyme. This ORF was identified as thepadAgene. A second ORF was located just downstream of thepadAgene and displayed 37% identity with the product of theBacillus subtilis yfiOgene. Subcloning, transcriptional analysis, and expression studies withEscherichia coliof these two genes under thepadAgene promoter, demonstrated that the genes are organized in an autoregulated bicistronic operonic structure and that the gene located upstream of thepadAgene encodes the transcriptional repressor of thepadAgene. Transcription of thispadoperon inP. pentosaceusis acid phenol dependent.