Abstract: The chnB gene encoding a cyclohexanone monooxygenase was amplified by PCR from genomic DNA of Rhodococcus ruber JDM312,the PCR product was cloned into the pUC18 vector and sequenced,and the sequence identity searches were performed by using software Clustal X and Mega 3.1.The sequence analysis showed that the open reading frame of the chnB gene from Rhodococcus ruber JDM312 was 1 623 bp and codes for a polypeptide of 542 amino acids.DNA identities of the chnB genes between the JDM312 strain and the previously reported four other stains of Rhodococcus was 85% to 98%,and the phylogenic tree showed that these strains clustered one main branch.It can be concluded that the chnB gene of Rhodococcus ruber JDM312 is useful to further study on expression of cyclohexanone monooxygenase and its enzymatic activity.

Key words: rhodococcus ruber；cyclohexanone monooxygenase；cloning , sequencing