GENETIC ORGANIZATION, NUCLEOTIDE-SEQUENCE AND REGULATION OF EXPRESSION OF GENES ENCODING PHENOL HYDROXYLASE AND CATECHOL 1,2-DIOXYGENASE INACINETOBACTER-CALCOACETICUS NCIB8250

We have mutated Acinetobacter calcoaceticus NCIB-8250 to growth defici ency on phenol as sole carbon source and isolated genes with similarit y to phenol hydroxylase and catechol 1,2-dioxygenase by complementatio n. Sequence analysis reveals the presence of six open reading frames ( ORFs) with similarities to a Pseudomonas multicomponent phenol hydroxy lase which are followed by an ORF with similarity to catA from A. calc oaceticus ADP1. Transformation of these genes to ADP1 confers the abil ity to grow at the expense of phenol as sole carbon source. Primer ext ension analysis indicates phenol-inducible transcription from an RpoN- dependent promoter sharing sequence similarity with the sigma(54) cons ensus promoter sequence, except that the -12 box is GG instead of GC. A catA::lacZ transcriptional fusion shows the same induction profile f or beta-galactosidase expression as transcription from the sigma(54)-d ependent promoter. This result suggests that catA is cotranscribed in the same operon with the phenol hydroxylase-encoding genes and is cons istent with the fact that no apparent additional promoter is found for catA by sequence analysis or primer extension. Catechol 1,2-dioxygena se activity is induced in NCIB8250 by benzoate, whereas beta-galactosi dase expression from the catA::lacZ fusion is not. This observation le ads to the hypothesis that two differentially regulated catA genes sho uld be present in that strain.