Screening and function analysis of a cyclohexanone-degrading bacterium CN1 from deep sea sediment

Abstract:

Micrococcu luteus CN1 was found to be able to utilize cyclohexanone well from the strains originally isolated from Pacific Ocean sediment. The optimum conditions for its growth were determined as 25℃-37℃，pH 8，salinity 6%. It could survive in the medium with high concentration of cyclohexanone (>44% V/V), and grew most vigorously in medium with 16.7%(V/V) cyclohexanone. CN1 could transform cyclohexanol to cyclohexanone which could be further degraded and mineralized quickly. This indicated the presence of cyclohexanol dehydrogenase and probable presence of cyclohexanone monooxygenase. With degenerate PCR for cloning part of cyclohexanone monooxygenase gene,the DNA fragment of 450bp was gotten. Amino acid sequence analysis showed that it owned the conserved sequence of the Baeyer-Villiger monooxygenase family and had the highest homology of 80% with cyclohexanone monooxygenase from Arthrobacter sp.BP2, only 53% with that from Acinetobacter sp. NCIMB 9871 which had been the most deeply investigated. So far as we know, both cyclohexanol and cyclohexanone degradation resorted to cyclohexanone monooxygenase. So this gene should be responsible for cyclohexanone degradation in CN1. All the cyclohexanone-degraders previously reported could degrade cyclopentanone, but, CN1 did not degrade cyclopentanone. This indicated that cyclohexanone monooxygenase in CN1 was special. Additionally, it was found for the first time that cyclohexanol could inhibit cyclohexanone degradation to certain degree in CN1.