Analyses of both the alkB Gene Transcriptional Start Site and alkB Promoter-Inducing Properties of Rhodococcus sp. Strain BCP1 Grown on n -Alkanes

Rhodococcus sp. strain BCP1, known for its capacity to grow on short-chainn -alkanes (C2 to C7 ) and to cometabolize chlorinated solvents, was found to also utilize medium- and long-chainn -alkanes (C12 to C24 ) as energy and carbon sources. To examine this feature in detail, a chromosomal region which includes thealkB gene cluster encoding a non-heme di-iron monooxygenase (alkB ), two rubredoxins, and one rubredoxin reductase was cloned from the BCP1 genome. Furthermore, the activity of thealkB gene promoter (PalkB ) was examined in the presence of gaseous, liquid, and solidn -alkanes along with intermediates of the putativen -alkane degradation pathway. A recombinant plasmid, pTPalkB LacZ, was constructed by inserting thelacZ gene downstream of PalkB , and it was used to transformRhodococcus sp. strain BCP1. Measurements of β-galactosidase activity showed that PalkB is induced by C6 to C22 n -alkanes. Conversely, C2 to C5 and >C22 n -alkanes and alkenes, such as hexene, were not inducers ofalkB expression. The effects on PalkB expression induced by alternative carbon sources along with putative products ofn -hexane metabolism were also evaluated. This report highlights the great versatility ofRhodococcus sp. strain BCP1 and defines for the first time thealkB gene transcriptional start site and thealkB promoter-inducing capacities for substrates different fromn -alkanes in aRhodococcus strain.