Role of <i>Acinetobacter baylyi</i> Crc in Catabolite Repression of Enzymes for Aromatic Compound Catabolism

<jats:title>ABSTRACT</jats:title> <jats:p> Here, we describe for the first time the Crc ( <jats:italic>c</jats:italic> atabolite <jats:italic>r</jats:italic> epression <jats:italic>c</jats:italic> ontrol) protein from the soil bacterium <jats:italic>Acinetobacter baylyi</jats:italic> . Expression of <jats:italic>A. baylyi crc</jats:italic> varied according to the growth conditions. A strain with a disrupted <jats:italic>crc</jats:italic> gene showed the same growth as the wild type on a number of carbon sources. Carbon catabolite repression by acetate and succinate of protocatechuate 3,4-dioxygenase, the key enzyme of protocatechuate breakdown, was strongly reduced in the <jats:italic>crc</jats:italic> strain, whereas in the wild-type strain it underwent strong catabolite repression. This strong effect was not based on transcriptional regulation because the transcription pattern of the <jats:italic>pca-qui</jats:italic> operon (encoding protocatechuate 3,4-dioxygenase) did not reflect the derepression in the absence of Crc. <jats:italic>pca-qui</jats:italic> transcript abundance was slightly increased in the <jats:italic>crc</jats:italic> strain. Lack of Crc dramatically increased the mRNA stability of the <jats:italic>pca-qui</jats:italic> transcript (up to 14-fold), whereas two other transcripts ( <jats:italic>pobA</jats:italic> and <jats:italic>catA</jats:italic> ) remained unaffected. <jats:italic>p</jats:italic> -Hydroxybenzoate hydroxylase activity, encoded by <jats:italic>pobA</jats:italic> , was not significantly different in the absence of Crc, as protocatechuate 3,4-dioxygenase was. It is proposed that <jats:italic>A. baylyi</jats:italic> Crc is involved in the determination of the transcript stability of the <jats:italic>pca-qui</jats:italic> operon and thereby effects catabolite repression. </jats:p>