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Microorganisms. 2019 Oct 23;7(11). pii: E479. doi: 10.3390/microorganisms7110479.

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

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Department of Bioengineering, Nagaoka University of Technology, Nagaoka 940-2188, Japan
Department of Bioengineering, Nagaoka University of Technology, Nagaoka 940-2188, Japan.


Gram-positive actinomycete Rhodococcus jostii RHA1 is able to grow on C10 to C19 n-alkanes as a sole source of carbon and energy. To clarify, the n-alkane utilization pathway-a cluster of 5 genes (alkBrubA1A2BalkU) which appeared to be involved in n-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 n-alkane. Inactivation of alkB led to the absence of the ability to utilize n-undecane. The alkB mutation resulted in reduction of growth rates on C10 and C12 n-alkanes; however, growths on C13 to C19 n-alkanes were not affected by this mutation. These results suggested that alkB was essential for the utilization of C10 to C12 n-alkanes. Inactivation of alkU showed the constitutive expression of alkB. Purified AlkU is able to bind to the putative promoter region of alkB, suggesting that AlkU played a role in repression of the transcription of alk operon. The results of this study indicated that alkB was involved in the medium-chain n-alkanes degradation of strain RHA1 and the transcription of alk operon was negatively regulated by alkU-encoded regulator. This report is important to understand the n-alkane degradation pathway of R. jostii, including the transcriptional regulation of alk gene cluster.


Rhodococcus; TetR-type transcriptional regulator; n-alkane; n-alkane hydroxylase

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Conflict of interest statement

No potential conflict of interest was reported by the authors. The funders had no role in the decision to publish the results.

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