Characterization and Transcriptional Regulation of n -Alkane Hydroxylase Gene Cluster of Rhodococcus jostii RHA1

Gram-positive actinomycete RHA1 is able to grow on C10 to C19 -alkanes as a sole source of carbon and energy. To clarify, the -alkane utilization pathway-a cluster of 5 genes ( ) which appeared to be involved in -alkane degradation-was identified and the transcriptional regulation of these genes was characterized. Reverse transcription-PCR analyses revealed that these genes constituted an operon and were transcribed in the presence of -alkane. Inactivation of led to the absence of the ability to utilize -undecane. The mutation resulted in reduction of growth rates on C10 and C12 -alkanes; however, growths on C13 to C19 -alkanes were not affected by this mutation. These results suggested that was essential for the utilization of C10 to C12 -alkanes. Inactivation of showed the constitutive expression of . Purified AlkU is able to bind to the putative promoter region of , suggesting that AlkU played a role in repression of the transcription of operon. The results of this study indicated that was involved in the medium-chain -alkanes degradation of strain RHA1 and the transcription of operon was negatively regulated by -encoded regulator. This report is important to understand the -alkane degradation pathway of , including the transcriptional regulation of gene cluster.