Two genes encoding proteins with similarities to rubredoxin and rubredoxin reductase are required for conversion of dodecane to lauric acid in Acinetobacter calcoaceticus ADP1

摘要

Mutants of Acinetobacter calcoaceticus ADP1 unable to grow on dodecane, but retaining the ability to grow on lauric acid were isolated after ethylmethanesulphonate (EMS) treatment. This growth deficiency was complemented by a clone from a gene library constructed from chromosomal DNA of the wild-type strain. The complementing DNA mapped in a gene encoding a polypeptide with homology to rubredoxins. The deduced putative rubredoxin amino acid sequence is more similar to related proteins from Gram-positive bacteria than to the Pseudomonas oleovorans rubredoxin involved in alkane oxidation. An adjacent gene encodes a protein with similarity to rubredoxin reductase from Pseudomonas oleovorans and related NAD(P)-dependent reductases. Disruption of the rubredoxin-encoding gene by insertion of a KmR/lacZ cassette rendered the resulting strain unable to grow on dodecane or hexadecane. This demonstrates that these genes are necessary for alkane degradation. Transcriptional fusion of lacZ to the rubredoxin-encoding gene led to low level constitutive β-galactosidase expression, whereas the fusion oriented in the opposite direction was not expressed.