Yang X, Liu X, Song L, Xie F, Zhang G, Qian S
State Key Laboratories of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
J Appl Microbiol. 2007 Dec;103(6):2214-24. doi: 10.1111/j.1365-2672.2007.03461.x.
Isolation of the genes relative to PCB biodegradation and identification of the bph gene function in Rhodococcus sp. R04.
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.
The cloned bph genes indeed play an important role in the biphenyl catabolism in this strain.
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.
分离与多氯联苯生物降解相关的基因，并鉴定红球菌属R04中bph基因的功能。
从红球菌属R04的基因文库中分离出一个携带联苯分解代谢基因bphABCD的8.7 kb片段。根据推导的氨基酸序列同源性，认为7个bph基因，即bphA1A2A3A4、bphB、bphC和bphD，负责联苯降解的最初四个步骤。在大肠杆菌中，BphA对联苯转化的活性较差，而BphB、BphC和BphD分别对2,3 - 二氢 - 2,3 - 二羟基联苯、2,3 - 二羟基联苯和2 - 羟基 - 6 - 氧代 - 6 - 苯基己 - 2,4 - 二烯酸具有催化活性（活性分别为50、8.1和2.4 μmol l(-1) min(-1) mg(-1)）。SDS - PAGE分析表明，bphA1A2A3A4、bphB、bphC和bphD基因产物的大小分别为49、19、14、47、32、30和31 kDa。bph基因被破坏后，bphA1突变体失去了在联苯上生长的能力，bphB和bphD突变体能够转化少量联苯，但几乎不能在联苯上生长。
克隆的bph基因确实在该菌株的联苯分解代谢中起重要作用。
红球菌属R04中的这种bph基因组织与先前报道的其他联苯降解菌不同，表明它是一种新型的bph基因簇。系统发育树分析表明，红球菌属R04中的BphA1和BphA2与其他多氯联苯降解菌中的BphA1和BphA2具有不同的进化关系。
