Distribution of alkB genes within n‐alkane‐degrading bacteria

Fifty‐four bacterial strains belonging to 37 species were tested for their ability to assimilate short chain and/or medium chain liquid n‐alkanes. A gene probe derived from the alkB gene of Pseudomonas oleovorans ATCC 29347 was utilized in hybridization experiments. Results of Southern hybridization of PCR‐amplificates were compared with those of colony hybridization and dot blot hybridization. Strongest signals were received only from Gram‐negative bacteria growing solely with short n‐alkanes (C10). Hybridization results with soil isolates growing with n‐alkanes of different chain lengths suggested as well that alkB genes seem to be widespread only in solely short‐chain n‐alkane‐degrading pseudomonads. PCR products of Rhodococcus sp., Nocardioides sp., Gordona sp. and Sphingomonas sp. growing additionally or solely with medium‐chain n‐alkane as hexadecane had only few sequence identity with alkB though hybridizing with the gene probe. The derived amino acid sequence of the alkB‐amplificate of Pseudomonas aureofaciens showed high homology (95%) with AlkB from Ps. oleovorans. alkB gene disruptants were not able to grow with decane.