SYNTHESIS OF ALKANE HYDROXYLASE OF PSEUDOMONAS-OLEOVORANS INCREASES THE IRON REQUIREMENT OF ALK(+) BACTERIAL STRAINS

The alk genes enable Pseudomonas oleovorans to utilize alkanes as sole carbon and energy source, Expression of the alk genes in P., oleovora ns and in two Escherichia coli recombinants induced iron limitation in minimal medium cultures. Further investigation showed that the expres sion of the alkB gene, encoding the integral cytoplasmic membrane prot ein AlkB, was responsible for The increase of the iron requirement of E. coli W3110 (pGEc47). AlkB is the non-heme iron monooxygenase compon ent of the alkane hydroxylase system, and can be synthesized to levels up to 10% (w/w) of total cell protein in E. call W3110 (pGEc47), Its synthesis is, however; strictly dependent on the presence of sufficien t iron in the medium. Our results show that a glucose-grown E. coli al k(+) strain can reach alkane hydroxylase activities of about 25 U/g cd w, and are consistent with the recent finding that catalytically activ e AlkB contains two, rather than one iron atom per polypeptide chain. (C) 1998 John Wiley & Sons, Inc.