Corkery D M, Dobson A D
Microbiology Department, University College Cork, Ireland.
FEMS Microbiol Lett. 1998 Sep 15;166(2):171-6. doi: 10.1111/j.1574-6968.1998.tb13886.x.
Pseudomonas fluorescens strain CA-4 is a bioreactor isolate previously characterised by the presence of a side chain oxidation pathway for ethylbenzene breakdown. In this report a second pathway involving ethylbenzene ring dioxygenation has been identified in this strain. We examine here second substrate inhibition of the genes encoding the initial enzymes of this pathway, using reverse transcription (RT)-PCR. The genes of the ring-dioxygenation have been cloned and sequenced. They exhibit near identity to the gene clusters encoding the aromatic ring dioxygenase enzymes of two previously described isopropyl degrading strains, Pseudomonas sp. strain JR1 and P. fluorescens IP01. This dioxygenase pathway appears to be the major pathway for ethylbenzene degradation in this strain. The expression of these genes appears to be affected by the presence of second carbon substrates. Using RT-PCR we demonstrate that the negative effect of glutamate present in the growth medium together with ethylbenzene on the rate of ethylbenzene metabolism is mediated at the transcriptional level on the ethylbenzene dioxygenase genes.
荧光假单胞菌CA-4菌株是一种从生物反应器中分离出的菌株，此前已通过存在乙苯分解的侧链氧化途径进行了表征。在本报告中，该菌株中鉴定出了第二条涉及乙苯环双加氧作用的途径。我们在此使用逆转录（RT）-PCR研究该途径初始酶编码基因的二次底物抑制作用。环双加氧作用的基因已被克隆和测序。它们与之前描述的两种异丙基降解菌株——假单胞菌属JR1菌株和荧光假单胞菌IP01菌株——编码芳香环双加氧酶的基因簇几乎完全相同。这种双加氧酶途径似乎是该菌株中乙苯降解的主要途径。这些基因的表达似乎受到第二种碳底物存在的影响。使用RT-PCR，我们证明生长培养基中存在的谷氨酸与乙苯一起对乙苯代谢速率的负面影响是在乙苯双加氧酶基因的转录水平上介导的。
