Characterization and functional analysis of a novel gene cluster involved in biphenyl degradation in Rhodococcus sp. strain R04.
OBJECTIVE
Isolation of the genes relative to PCB biodegradation and identification of the bph gene function in Rhodococcus sp. R04.


RESULTS
A 8.7-kb fragment carrying the biphenyl catabolic genes bphABCD was isolated from the gene library in Rhodococcus sp. R04. Based on the deduced amino acid sequence homology, seven bph genes, bphA1A2A3A4, bphB, bphC and bphD, were thought to be responsible for the initial four steps of biphenyl degradation. In Escherichia coli, BphA exhibited poor activity for biphenyl transformation, and BphB, BphC and BphD were found to be catalytically active towards 2,3-dihydro-2,3-dihydroxybiphenyl, 2,3-dihydroxybiphenyl and 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate, respectively (activities of 50, 8.1 and 2.4 micromol l(-1) min(-1) mg(-1)). SDS-PAGE analysis indicated that the sizes of bphA1A2A3A4, bphB, bphC and bphD gene products were 49, 19, 14, 47, 32, 30 and 31 kDa, respectively. After disruption of bph genes, the bphA1 mutants lost the ability to grow on biphenyl, the bphB and bphD mutants were able to transform a little of biphenyl, but hardly grew on biphenyl.


CONCLUSIONS
The cloned bph genes indeed play an important role in the biphenyl catabolism in this strain.


CONCLUSIONS
This bph gene organization in Rhodococcus sp. R04 differs from that of other biphenyl degraders reported previously, indicating it is a novel type of bph gene cluster. Analysis of the phylogenetic tree suggested that BphA1 and BphA2 in Rhodococcus sp. R04 had a different evolutionary relationship with those in the other PCB degraders.
Yang
X
X
State Key Laboratories of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
Liu
X
X
Song
L
L
Xie
F
F
Zhang
G
G
Qian
S
S
D000595:Amino Acid Sequence; D001431:Bacteriological Techniques; D001483:Base Sequence; D001673:Biodegradation, Environmental; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015723:Gene Library; D007218:Industrial Microbiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D011078:Polychlorinated Biphenyls / Q000378:metabolism*; D012240:Rhodococcus / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D011078:Polychlorinated Biphenyls