Involvement of an Alkane Hydroxylase System of Gordonia sp. Strain SoCg in Degradation of Solid n -Alkanes

Enzymes involved in oxidation of long-chainn -alkanes are still not well known, especially those in Gram-positive bacteria. This work describes the alkane degradation system of then -alkane degrader actinobacteriumGordonia sp. strain SoCg, which is able to grow onn -alkanes from dodecane (C12 ) to hexatriacontane (C36 ) as the sole C source. SoCg harbors in its chromosome a singlealk locus carrying six open reading frames (ORFs), which shows 78 to 79% identity with the alkane hydroxylase (AH)-encoding systems of other alkane-degrading actinobacteria. Quantitative reverse transcription-PCR showed that the genes encoding AlkB (alkane 1-monooxygenase), RubA3 (rubredoxin), RubA4 (rubredoxin), and RubB (rubredoxin reductase) were induced by bothn -hexadecane andn -triacontane, which were chosen as representative long-chain liquid and solidn -alkane molecules, respectively. Biotransformation ofn -hexadecane into the corresponding 1-hexadecanol was detected by solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME/GC-MS) analysis. TheGordonia SoCgalkB was heterologously expressed inEscherichia coli BL21 and inStreptomyces coelicolor M145, and both hosts acquired the ability to transformn -hexadecane into 1-hexadecanol, but the corresponding long-chain alcohol was never detected onn -triacontane. However, the recombinantS. coelicolor M145-AH, expressing theGordonia alkB gene, was able to grow onn -triacontane as the sole C source. A SoCgalkB disruption mutant that is completely unable to grow onn -triacontane was obtained, demonstrating the role of an AlkB-type AH system in degradation of solidn -alkanes.